tag:blogger.com,1999:blog-56412064221916651762024-02-19T15:56:28.671+08:00Lee Tat Leong's Physics BlogUnknownnoreply@blogger.comBlogger31125tag:blogger.com,1999:blog-5641206422191665176.post-9953411247364946562014-05-15T07:13:00.000+08:002014-05-15T07:13:15.145+08:00Summary of Nuclear Physics<iframe allowfullscreen="" frameborder="0" height="613" marginheight="0" marginwidth="0" scrolling="no" src="http://www.slideshare.net/slideshow/embed_code/34655164" style="border-width: 1px 1px 0; border: 1px solid #CCC; margin-bottom: 5px; max-width: 100%;" width="574"> </iframe> <br />
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<strong> <a href="https://www.slideshare.net/tatlee08/nuclear-physics-summary" target="_blank" title="Nuclear Physics Summary">Nuclear Physics Summary</a></strong></div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-62107887463828813422014-05-15T07:12:00.002+08:002014-05-15T07:12:22.861+08:00Quantum Physics Summary<iframe allowfullscreen="" frameborder="0" height="613" marginheight="0" marginwidth="0" scrolling="no" src="http://www.slideshare.net/slideshow/embed_code/34655160" style="border-width: 1px 1px 0; border: 1px solid #CCC; margin-bottom: 5px; max-width: 100%;" width="574"> </iframe> <br />
<div style="margin-bottom: 5px;">
<strong> <a href="https://www.slideshare.net/tatlee08/quantum-physics-summary" target="_blank" title="Quantum Physics Summary">Quantum Physics Summary</a></strong></div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-48080205288748247152014-04-13T08:39:00.000+08:002014-04-13T08:39:02.773+08:00Do you know the answer to this question?This is a billion dollar question. Do you have the answer?<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVfr4ZCEVdmXSLEBBgP0MOGPu2hXPmZN61d5bDFrc_B9VMK_g3KK60K45PqVjt6fFccwUehE2V-lvacqWdJ05tijEgh0y6AEAg8MZX-rijEKmFdTNVPqW0BntRzEST90VMGpMigWECh9jQ/s1600/Louisiana+Maths+Quiz.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhVfr4ZCEVdmXSLEBBgP0MOGPu2hXPmZN61d5bDFrc_B9VMK_g3KK60K45PqVjt6fFccwUehE2V-lvacqWdJ05tijEgh0y6AEAg8MZX-rijEKmFdTNVPqW0BntRzEST90VMGpMigWECh9jQ/s1600/Louisiana+Maths+Quiz.png" height="616" width="640" /></a></div>
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This question is extracted from <a href="http://www.louisianabelieves.com/resources/library/practice-tests" target="_blank">Department of Louisiana</a> 2013-2014 practice test for Grade 8 Maths and I was aware of this question through <a href="http://www.wired.com/2014/03/good-math-question/" target="_blank">Rhett Allain's</a> blog.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-91804191824643718112014-03-23T07:30:00.001+08:002014-03-23T07:30:56.685+08:00The Universe in a Nutshell - Michio KakuThis is probably one of the most concise, most interesting, most informative and most layman introduction to the four fundamental forces that I have watched. It kept me riveted to the screen for 42 mins even though I knew every facts explained in the video.<br />
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This video is a must for upper secondary and junior college students to watch as an introduction to the four fundamental forces and a brief glimpse of the wonder and beauty of Physics. It should replace the boring five minutes we accord to the fundamental forces when we lecture.<br />
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<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/0NbBjNiw4tk?rel=0" width="560"></iframe>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-28567880063252151602014-03-05T20:40:00.002+08:002014-03-05T20:40:30.193+08:00Finding analogies to abstract Physics conceptsThis is a hilarious method to introduce the atom to a gangster. However it works! In learning we need to find our personal analogies to have enduring understanding.<br />
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<iframe allowfullscreen="" frameborder="0" height="360" src="//www.youtube.com/embed/YDxUzU4wqeQ?rel=0" width="480"></iframe>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-21693058293734989352014-02-14T21:57:00.000+08:002014-02-14T21:57:36.833+08:00How is energy being transferred in a conventional circuit? A new but coherent perspective.I saw this videos some years ago and shared with my graduating class students even though it is not the usual way energy transferred in circuits is being taught and assessed.<br />
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<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/QQ6aRfJKODE" width="560"></iframe><br />
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Two days ago, I watched this video again while searching for videos for Quantum Physics. I was determined to find out how energy can be transferred outside the wire!<br />
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Few interesting concepts from my internet research, some was new to me before my research:<br />
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<ul>
<li>The battery (source) causes a different distribution of surface charges along the circuit, this indicate a slightly non-neutrally along short sections in the circuit. This is possible as there is dynamic equilibrium (analogous to a pressure gradient in fluid flow in pipes) in the circuit. <i><span style="color: red;">Conventional teaching claims that the entire circuit is neutral because the net charge is zero, which is correct, but we incorrectly extend it to mean that every section of the wire must be neutral.</span></i></li>
<li>The distribution of surface charges result in (a) an electric field along the wire and (b) electrostatic field that extend radially from the wire.</li>
<li>The electric field along the wire is what we normally associate as the potential difference between two points in a circuit (remember that E = -dV/dr). </li>
<li>The magnetic field associated with the movement charges in the wire is perpendicular (tangential to "circles" around the wire) to the radial electric field due to the surface charges. </li>
<li>The cross product E x B gives the Poynting vector that gives the direction of energy flow/transfer. This is how energy is transferred through space outside the wire!</li>
</ul>
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The following are some of the articles I have gathered the past two days:<br />
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<ul>
<li><a href="http://www.furryelephant.com/content/electricity/visualizing-electric-current/surface-charges-poynting-vector/" target="_blank">Surface Charges and Poynting Vector</a> - Relatively easy to understand the surface charge distribution.</li>
<li><a href="http://hyperphysics.phy-astr.gsu.edu/hbase/waves/emwv.html" target="_blank">HyperPhysics Poynting Vector</a> - Introduction to Poynting Vector.</li>
<li><a href="http://www.ippp.dur.ac.uk/~davis/EnergyTransferElectricCircuits.pdf" target="_blank">Energy transfer in electrical circuits: A qualitative account</a>, Igal Galili and Elisabetta Goihbarg - Article from Americal Journal of Physics which is very reputable and I would consider it to be a trustworthy source.</li>
<li><a href="http://www.matterandinteractions.org/Content/Articles/circuit.pdf" target="_blank">A unified treatment of electrostatics and circuits</a>, B. A. Sherwood and R. W. Chabay - a more detail development of the concepts compared to the previous Am. J. Phys. article. Possibly a guide for teachers who want to challenge their students' understanding of circuits.</li>
</ul>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-37046012470629764902014-02-11T13:58:00.001+08:002014-02-11T13:58:21.676+08:00Pre-lecture activity on Quantum Physics<iframe frameborder="0" height="500" marginheight="0" marginwidth="0" src="https://docs.google.com/forms/d/1PFNgf_nYASZy8XcYqhBc3hcq-Bn0s9Ej2-UvQDW3hHk/viewform?embedded=true" width="600">Loading...</iframe>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-49935887810320592702014-02-11T00:15:00.001+08:002014-02-11T06:49:26.701+08:00Current Balance Demonstration/Experiment<div>
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Photo above showing the wire frame where current will pass through. The frame is completely between the poles of the u-shaped magnet (North is red) during experiment.</div>
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Photo above shows that the wire frame is not in contact with the magnet. </div>
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The video of the experiment is embedded below or <a href="http://youtu.be/nkS7wCCzGiY">http://youtu.be/nkS7wCCzGiY</a>. You may pause the video at each current reading to obtain the following data. The balance is zeroed to measure ony the gain/loss in mass of magnet.<br />
<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/nkS7wCCzGiY?rel=0" width="560"></iframe>
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<span style="font-family: inherit;"><i>Questions: What is the direction of the force on the wire frame and the magnet? Why is the magnet getting "heavier"? When the current is reversed (</i><a href="http://youtu.be/hnU4g4NBXXo">http://youtu.be/hnU4g4NBXXo</a><i>), why is the magnet getting "lighter"?</i></span></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDoPx-qdVa-Yw-3Ri_o3nLtD4jnmkMquNdAoHBPwBHTb6P-lbUo230_KF55VjzjOSjfhi7lTPMcXb7vtz9JPp6rswrK2duBKGOJzgXcaFZDeTEqn0-mYRy5wkvZXquWw5BXXL4_EAwcWeW/s640/blogger-image-1405176652.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="262" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgDoPx-qdVa-Yw-3Ri_o3nLtD4jnmkMquNdAoHBPwBHTb6P-lbUo230_KF55VjzjOSjfhi7lTPMcXb7vtz9JPp6rswrK2duBKGOJzgXcaFZDeTEqn0-mYRy5wkvZXquWw5BXXL4_EAwcWeW/s320/blogger-image-1405176652.jpg" width="320" /></a></div>
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The electronic balance gives reading in grammes. The magnetic force is obtained by multiplying the balance reading by 10 N/kg (or 9.8 N/kg if you want to be accurate). Since</div>
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<b>F = BIL</b></div>
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Plot a graph of magnetic force F against current I in the wire frame. If a linear trend is obtained, the gradient will be BL where L is measured to be 4.0 cm. </div>
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Gradient = 4.466 mN/A = 0.004466 N/A</div>
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Therefore B = 0.004466/0.040 = 0.11 T</div>
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This value is reasonable because the magnetic flux density of the magnet should be much greater than Earth's intrinsic magnetic field (~10 nT) and flux density of more than 1 T is hard to obtain in common school lab.</div>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-8167106585615516572014-02-10T23:35:00.001+08:002014-02-10T23:35:50.743+08:00Demonstrations and questions on electrons in electric or magnetic field<h2>
Demo 1 - Increasing deflection plates potential difference</h2>
<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/8WLc7DeLdzg?rel=0" width="420"></iframe>
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Questions:<br />
<ul>
<li>What do you notice about the electron beam when the deflection plates p.d. is increased?</li>
<li>Explain your answer to the previous question.</li>
</ul>
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<b>Demo 2 - Increasing accelerating potential </b></h2>
<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/DQa7A4t-EgQ?rel=0" width="420"></iframe>
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Questions:<br />
<ul>
<li>What do you notice about the electron beam when the accelerating p.d. is increased?</li>
<li>Explain your answer to the previous question.</li>
</ul>
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Demo 3 - Electron beam in uniform magnetic field while accelerating potential is increased</h2>
<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/9n08d5Hqfqk?rel=0" width="420"></iframe><br />
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Questions:<br />
<ul>
<li>What do you notice about the electron beam in uniform when the accelerating potential is increased?</li>
<li>Explain your answer to the previous question.</li>
</ul>
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Demo 4 - Electron in increasing magnetic field</h2>
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<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/KsvcCx_xh38?rel=0" width="420"></iframe>
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Questions:<br />
<ul>
<li>What do you notice about the electron beam in uniform field when magnetic flux density is increased?</li>
<li>Explain your answer to the previous question.</li>
</ul>
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Demo 5 - Electrons enter the magnetic field not at right angle (Helical motion)</h2>
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Questions:<br />
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<li>What do you notice about the electron enter the magnetic field not at right angle?</li>
<li>Explain your answer to the previous question. The video below may help you.</li>
</ul>
<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/a2_wUDBl-g8?rel=0" width="420"></iframe>
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<br />Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-53376699353587680902014-01-23T16:47:00.002+08:002014-01-23T16:47:53.744+08:00How does a potentiometer work?<iframe frameborder="0" height="433" src="https://www.showme.com/sma/embed/?s=txNptj6" width="578"></iframe>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-55395224120676326872013-07-05T07:12:00.000+08:002013-07-05T09:26:32.645+08:00Feynman on kinetic modelThis week I am doing work and energy with my Y3 students. We started with the concept of work and went on to the activity bouncing ball activity shown below.<br />
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Bouncing Ball Activity</h2>
<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/1oSb7Ilx9mM" width="420"></iframe><br />
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<b>Explain</b>:</div>
<ul>
<li>Describe the conversion of energies during the motion from point of release to just before hitting the surface </li>
<li>Explain why the returned height after each bounce is less</li>
</ul>
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Students' explanation on why the ball has a lower height after each bounce</h2>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjT_m5TOtZS3HDEpdQAiOWm5IWJ0goaSDrEJWem4eDIIqwkD-3xXGho9A_cIhgTOMOZuY5UQsM2QtEj6kkMAzjtwYdxU1uCTpVttbCJUOlNPv2QIbXIPWJhsURYP0M2gGD_yQoX4DCfw6At/s800/IMG_1482.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="228" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjT_m5TOtZS3HDEpdQAiOWm5IWJ0goaSDrEJWem4eDIIqwkD-3xXGho9A_cIhgTOMOZuY5UQsM2QtEj6kkMAzjtwYdxU1uCTpVttbCJUOlNPv2QIbXIPWJhsURYP0M2gGD_yQoX4DCfw6At/s400/IMG_1482.JPG" width="400" /></a></div>
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It is a rather common for learners to associate any lost in mechanical energy as "being converted to heat". It is probably because of the fact that they have experienced the warmness due to phenomena such as rubbing their palms, hitting a nail, etc.</div>
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Qualitative understanding of the energy exchange during the bounce</h2>
What really happens requires the understanding of the following concepts:<br />
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<ul>
<li>Temperature is a macroscopic observable/measurable of the average kinetic energy of random molecular motion</li>
<li>The contact between the ball and the floor increases the random molecular motion at the expense of the ordered mechanical energy. This causes the temperature of the ball and floor to rise or we say that the internal energy of the system increases.</li>
<li>Assuming that the ball and floor is at thermal equilibrium to the surrounding, the increase in their temperatures result in a net transfer of heat to the surrounding, i.e. the warmness we feel if we are to touch them (the temperature difference is likely to be less than what we can perceive in reality).</li>
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In addition, we can also apply the same thinking to conclude that the movement of the ball through the air also increases the internal energy of both the ball and the surrounding air.</div>
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Feynman's explanation below (from about 1min45sec to 3min15sec) really sums it for learners and most importantly encourages them to enjoy thinking about science. <br />
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<iframe allowfullscreen="" frameborder="0" height="315" src="//www.youtube.com/embed/v3pYRn5j7oI" width="420"></iframe></div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-11081033021461396552013-06-24T10:48:00.000+08:002013-06-24T10:48:05.550+08:00Gowth MindsetFostering a growth mindset in learners (children, adults) may be one of the key to improve learner's motivation to learn, ownership of learning, perseverance, etc. As teachers, we may not have been tackling the root cause of these learning characteristics.<br />
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Learners will benefit greatly from a changed mindset about learning.<br />
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<b>The benefits of a Growth Mindset - Carol Dweck
</b><iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/arCdzdBhCcc" width="420"></iframe><br />
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<b>The Power of Belief - Mindset and Success: Eduardo Briceno at TEDxManhattanBeach</b>
<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/pN34FNbOKXc" width="560"></iframe>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-9360266453360736812013-06-21T16:51:00.005+08:002013-06-21T16:51:56.265+08:00Physics of HazeI couldn't help it but to apply what I know in Physics to explain the white/gray haze as a result of the smoke particles from the Sumatran fires.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizOK8iRRyUgd0M6GYcUYQSAbNI5UCFhE-D0PAi13D17lJMZBE4uCfizBKMOhpB3WxXOIJguqlGlhPM2qYkE1qaTHYnmfPRarIKvNVnLeFEZFJrAwmql7b6WtV33_LInQVbdAoS06BNfoo4/s1600/IMG_0778.JPG" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="181" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEizOK8iRRyUgd0M6GYcUYQSAbNI5UCFhE-D0PAi13D17lJMZBE4uCfizBKMOhpB3WxXOIJguqlGlhPM2qYkE1qaTHYnmfPRarIKvNVnLeFEZFJrAwmql7b6WtV33_LInQVbdAoS06BNfoo4/s320/IMG_0778.JPG" width="320" /></a></div>
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To begin, let's try to understand how we see the colours of the buildings and the trees. We "see" the colour of the light that is scattered off the surface of the building, leaves, etc, as shown.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX9McRcyukE-mqIR7qPO2W6ntbtM5qDrF_bfXZ9zpA_y-jTFNcwJ_chAGxPpR093IuL9g67bMk3onG9jiaRwu7eEHvEcgI5KhxZS3vX8LTwmTRCtsPlNXTngvHbQ62VqHOs8jtF-I3C9ib/s1600/scattering+of+haze+01.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiX9McRcyukE-mqIR7qPO2W6ntbtM5qDrF_bfXZ9zpA_y-jTFNcwJ_chAGxPpR093IuL9g67bMk3onG9jiaRwu7eEHvEcgI5KhxZS3vX8LTwmTRCtsPlNXTngvHbQ62VqHOs8jtF-I3C9ib/s400/scattering+of+haze+01.gif" width="378" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Scattering of light from surface (e.g. green wavelength em waves from the leaves) causes us to "see" the objects' colour</td></tr>
</tbody></table>
<div class="separator" style="clear: both; text-align: center;">
<br /></div>
Light is also scattered by the air molecules (~ nanometer in diameter) along the path from the sun to the object by a process known as Rayleigh Scattering (refer to my <a href="http://ltlphysics.blogspot.sg/2013/05/why-is-sky-blue.html" target="_blank">previous post</a>) towards the observer. However intensity from this scattering is low compare to the intensity of light reaching the objects and scattering to the observer. Generally our eyes cannot sense this low intensity in the presence of the light from the objects.<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEib-ITf68Z7xbf_C6aBlm9Y0xW2Ca5HEgTSbng0CV0kvRDG6dFHLieSsrh1X3L9g81y7uSCBdjNE8cvD-wxleUuspktI_k_DFoD9iLEBwpWkMMbForyPFdzbFdOZAxTRcXwRi7hKG50ZqbL/s1600/scattering+of+haze+02.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEib-ITf68Z7xbf_C6aBlm9Y0xW2Ca5HEgTSbng0CV0kvRDG6dFHLieSsrh1X3L9g81y7uSCBdjNE8cvD-wxleUuspktI_k_DFoD9iLEBwpWkMMbForyPFdzbFdOZAxTRcXwRi7hKG50ZqbL/s400/scattering+of+haze+02.gif" width="378" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Effect of Rayleigh Scattering is small and hence don't produce the white haze </td></tr>
</tbody></table>
<br />
With the dust particles, diameter in the region of microns (0.000001 m), suspended in the air, Mie scattering dominates. The scattering intensity by this process is larger than Rayleigh Scattering. The larger intensity of white light scattered from these particles (consisting of all visible wavelengths) is now more obvious to us.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfWiknEYpemioU3fswiGUR1gy6sa-oCIn263uZGxyj3-hnYEXFx6ToEnbte09cXSTlCbRdZBi5A2_kasi3Yc5WcP8d3hFX246U-xkV3PlFPmu0p_WaKeWXlE7ULj49yecTgG5Icb8ZLa5b/s1600/scattering+of+haze+03.gif" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgfWiknEYpemioU3fswiGUR1gy6sa-oCIn263uZGxyj3-hnYEXFx6ToEnbte09cXSTlCbRdZBi5A2_kasi3Yc5WcP8d3hFX246U-xkV3PlFPmu0p_WaKeWXlE7ULj49yecTgG5Icb8ZLa5b/s400/scattering+of+haze+03.gif" width="378" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Mie Scattering off the dust particles produces the white haze seen the above photo</td></tr>
</tbody></table>
The additional scattering also explain why the sky and the sun appears red around 6 pm, something we usually observe around 7pm when the sun is close to the horizon.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicuIITi488yUClquvCOchyphenhyphenpW4vNTIjvmrQi4CGvwEiCcWv359DEAtj0AQcoDRIVx8EmCQoxgF5cdTX2HM_efwoZ7gInL-mpADqfHuajx0qzbKavvGewxktKM57vwGl3Eu72AVET228yzqK/s1600/IMG_0776.JPG" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEicuIITi488yUClquvCOchyphenhyphenpW4vNTIjvmrQi4CGvwEiCcWv359DEAtj0AQcoDRIVx8EmCQoxgF5cdTX2HM_efwoZ7gInL-mpADqfHuajx0qzbKavvGewxktKM57vwGl3Eu72AVET228yzqK/s400/IMG_0776.JPG" width="298" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Red sky and sun around 6pm</td></tr>
</tbody></table>
<br />
For more information on the different type of scattering, you may want to refer to <a href="http://hyperphysics.phy-astr.gsu.edu/hbase/atmos/blusky.html" target="_blank">this</a>.Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-23860535270410192742013-06-20T09:03:00.002+08:002013-06-20T09:03:58.723+08:00Using Tracker to study solar spectrum (with absorption lines) for the topic of Quantum Physics<b>Line Spectral with Tracker</b><br />
Created this instructional video on "using Tracker for spectroscopy". Youtube link is <a href="http://youtu.be/QSgeoLgJQdo" target="_blank">here</a>.<br />
<br />
<iframe allowfullscreen="" frameborder="0" height="315" src="http://www.youtube.com/embed/QSgeoLgJQdo" width="560"></iframe>
<br />
<strong>Lessons that took place before this activity</strong>
Students could have
<br />
<ul>
<li>observed the emission spectrum of elements such as sodium, neon, mercury, kryption, etc. although they do not have hands-on experience of setting up and adjusting the apparatus.</li>
<li>gone through the theory and tutorial on the section of spectral lines.</li>
</ul>
<strong>Resources</strong><br />
Below is the worksheet that students will attempt.
<iframe allowfullscreen="" frameborder="0" height="613" marginheight="0" marginwidth="0" mozallowfullscreen="" scrolling="no" src="http://www.slideshare.net/slideshow/embed_code/12590593" style="border-width: 1px 1px 0; border: 1px solid #CCC; margin-bottom: 5px;" webkitallowfullscreen="" width="574"> </iframe> <br />
<div style="margin-bottom: 5px;">
<strong> <a href="http://www.slideshare.net/tatlee08/analysing-solar-spectrum" target="_blank" title="Analysing solar spectrum">Analysing solar spectrum</a> </strong> from <strong><a href="http://www.slideshare.net/tatlee08" target="_blank">Lee Tat Leong</a></strong> </div>
<br />
Pictures of the solar spectrum and the emission spectrum of different elements (derived from the picture <a href="http://galacticfool.com/solar-system/sun/" target="_blank">here</a> and <a href="http://www.amateurspectroscopy.com/color-spectra-of-chemical-elements.htm" target="_blank">here</a>).
<br />
<ul>
<li><a href="http://leetl.files.wordpress.com/2012/04/h.png" target="_blank">Hydrogen</a> (H)</li>
<li><a href="http://leetl.files.wordpress.com/2012/04/he.png" target="_blank">Helium</a> (He)</li>
<li><a href="http://leetl.files.wordpress.com/2012/04/na.png" target="_blank">Sodium</a> (Na)</li>
<li><a href="http://leetl.files.wordpress.com/2012/04/mg.png" target="_blank">Magnesium</a> (Mg)</li>
<li><a href="http://leetl.files.wordpress.com/2012/04/solar-spectrum.png" target="_blank">Solar spectrum</a></li>
</ul>
<strong>Disadvantages of hands-on approach</strong>
<br />
<ul>
<li>Experiments on spectral lines are time consuming due to the difficulty in setting up and calibrating the spectrometer.</li>
<li>The other big challenge is the availability of a suitably dark room to observe the emission spectrum of discharge tubes.</li>
<li>The availability of sufficient apparatus for experiments.</li>
</ul>
<strong>Advantages of using Tracker</strong>
<br />
<ul>
<li>Cheap.</li>
<li>Easy to deploy.</li>
<li>Easy to operate to obtain quality results for comparison and analysis because students can now focus on the actual physics rather than on the setting up of the experiment.</li>
</ul>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-41508586743331403942013-06-20T08:50:00.000+08:002013-06-20T08:51:33.383+08:00What is a Field?This is the Physicists' way of looking at the field concept. Kind of difficult for layman like us to understand. Enjoy :-)<br />
<embed base="http://admin.brightcove.com" bgcolor="#FFFFFF" flashvars="videoId=2492046910001&playerId=1399191810&viewerSecureGatewayURL=https://console.brightcove.com/services/amfgateway&servicesURL=http://services.brightcove.com/services&cdnURL=http://admin.brightcove.com&domain=embed&autoStart=false&" height="550" name="flashObj" pluginspage="http://www.macromedia.com/shockwave/download/index.cgi?P1_Prod_Version=ShockwaveFlash" seamlesstabbing="false" src="http://c.brightcove.com/services/viewer/federated_f8/1399191810" swliveconnect="true" type="application/x-shockwave-flash" width="510"></embed><br />
From <a href="http://www.scientificamerican.com/video.cfm?id=what-is-a-field2013-06-19" target="_blank">Scientific American</a>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-10466500119915303492013-05-31T20:32:00.003+08:002013-05-31T20:32:40.824+08:00Why is the sky blue?<div class="visually_embed" data-category="Science" rel="interactive">
<img alt="Why is the Sky Blue?" class="visually_embed_infographic" rel="http://thumbnails.visually.netdna-cdn.com/why-is-the-sky-blue_51a54f429a91e.png" src="http://thumbnails.visually.netdna-cdn.com/why-is-the-sky-blue_51a54f429a91e_w587.png" />
<br />
<div class="visually_embed_bar">
<span class="visually_embed_cycle"><a href="http://visual.ly/why-sky-blue-0/?utm_source=visually_embed">Why is the Sky Blue? infographic</a> by <a href="http://halftone.co/?utm_source=visually_embed" target="_blank">ptvan</a>. </span>
</div>
<a href="http://visual.ly/why-sky-blue-0?utm_source=visually_embed" id="visually_embed_view_more" target="_blank"></a>
<link href="http://visual.ly/embeder/style.css" rel="stylesheet" type="text/css"></link>
<script src="http://visual.ly/embeder/embed.js" type="text/javascript"></script>
</div>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-63954992103916632202013-05-18T04:13:00.002+08:002013-05-18T04:13:38.799+08:00Wheels are everywhere<div class="separator" style="clear: both; text-align: left;">
This is something that should be related to your experience when shopping with your family at supermarkets, etc. Observe the behaviour of the wheels and provide your responses to the questions after the video.</div>
<div class="separator" style="clear: both; text-align: left;">
<br /></div>
<div class="separator" style="clear: both; text-align: center;">
<iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/mZwHi1-lJ74?feature=player_embedded' frameborder='0'></iframe></div>
<br />
<iframe frameborder="0" height="500" marginheight="0" marginwidth="0" src="https://docs.google.com/forms/d/1hbQ1ptwQw2wCfg7m4NHmsO7HaKZ4oCHM02C7pKez_gg/viewform?embedded=true" width="760">Loading...</iframe>Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-37140860471020022622013-04-15T08:41:00.002+08:002013-04-15T08:41:27.156+08:00Common Misconceptions when using Newton’s 3rd Law of Motion
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<br />
<div class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph;">
<span style="font-family: Arial; font-size: 11.0pt;">Newton’s 3<sup>rd</sup> Law (N3L)
presents the greatest challenge to students unlike the first two laws of motion
because what it claims is contrary to many daily experiences and hence counter-intuitive.
Newton's Laws of motion allows us to break down the problem systematically by first
looking at the forces exerted on bodies, compute the resultant force and predict
its motion. <o:p></o:p></span></div>
<div class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph;">
<br /></div>
<div class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph;">
<span style="font-family: Arial; font-size: 11.0pt;">Challenges to learners include:<o:p></o:p></span></div>
<div class="MsoNormal" style="margin-left: 18.0pt; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -18.0pt; text-justify: inter-ideograph;">
<!--[if !supportLists]--><span style="font-family: Symbol; font-size: 11.0pt; mso-bidi-font-family: Symbol; mso-fareast-font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt;"> </span></span><b><span style="font-family: Arial; font-size: 11.0pt;">N3L only work for specific
situations, e.g., system at rest<o:p></o:p></span></b></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<i><span style="color: blue; font-family: Arial; font-size: 11.0pt;">In using N3L, we are looking only at the <b>forces between two bodies at the
point/surface of direct contact</b> (except for the fundamental forces which
are action-at-distance<a href="http://www.blogger.com/blogger.g?blogID=5641206422191665176#_ftn1" name="_ftnref1" title=""><span class="MsoFootnoteReference"><!--[if !supportFootnotes]--><span class="MsoFootnoteReference"><b><span style="color: blue; font-size: 11pt;">[1]</span></b></span><!--[endif]--></span></a>). If the <b>two bodies are in contact</b>, the <b>force on each body due to the other body</b>
must be equal and opposite. There is no need to look beyond the contact point
when using N3L. <o:p></o:p></span></i></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<br /></div>
<div class="MsoNormal" style="margin-left: 18.0pt; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -18.0pt; text-justify: inter-ideograph;">
<!--[if !supportLists]--><span style="font-family: Symbol; font-size: 11.0pt; mso-bidi-font-family: Symbol; mso-fareast-font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt;"> </span></span><b><span style="font-family: Arial; font-size: 11.0pt;">Object being pushed experience a
larger force exerted by the imparter (e.g., a person) while the force exerted
on the imparter by the object should “logically” be less. <o:p></o:p></span></b></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<i><span style="color: blue; font-family: Arial; font-size: 11.0pt;">This is a compromised version of N3L.
Students recognized and know that they need to apply N3L but preconceptions compel
students to come up with alternate N3L to accommodate daily experiences. The
single most difficult misconception to rectify in students since it is contrary
to daily experiences.<o:p></o:p></span></i></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<br /></div>
<div class="MsoNormal" style="margin-left: 18.0pt; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -18.0pt; text-justify: inter-ideograph;">
<!--[if !supportLists]--><span style="font-family: Symbol; font-size: 11.0pt; mso-bidi-font-family: Symbol; mso-fareast-font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt;"> </span></span><b><span style="font-family: Arial; font-size: 11.0pt;">Using N3L to describe the forces
acting on the same body<o:p></o:p></span></b></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<i><span style="color: blue; font-family: Arial; font-size: 11.0pt;">Forces like gravitational force (or
weight) and normal force exerted by the table are taken to be the pair of
forces in accordance to N3L because they are “equal and opposite”. <o:p></o:p></span></i></div>
<div class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph;">
<br /></div>
<div class="MsoNormal" style="margin-left: 18.0pt; mso-list: l0 level1 lfo1; text-align: justify; text-indent: -18.0pt; text-justify: inter-ideograph;">
<!--[if !supportLists]--><span style="font-family: Symbol; font-size: 11.0pt; mso-bidi-font-family: Symbol; mso-fareast-font-family: Symbol;">·<span style="font-family: 'Times New Roman'; font-size: 7pt;"> </span></span><b><span style="font-family: Arial; font-size: 11.0pt;">Dealing with massless string<o:p></o:p></span></b></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<i><span style="color: blue; font-family: Arial; font-size: 11.0pt;">In basic mechanics, the sole purpose of
the string is to connect various bodies so that they behave as a single system
yet they are not in contact. N3L is not applicable to the forces between two
bodies even though they satisfy “equal and opposite forces on two different
bodies” condition because they are not in contact. N3L describe the pair forces
between each end of the string with the body. For the string, the forces on
both ends must cause it to be taut and have equal magnitude regardless of the
state of motion of the system. This is a consequence of Newton’s 2<sup>nd</sup>
Law<o:p></o:p></span></i></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<i><span style="color: blue; font-family: Arial; font-size: 11.0pt;">
Resultant force on string = mass x acceleration<o:p></o:p></span></i></div>
<div class="MsoNormal" style="margin-left: 18.0pt; text-align: justify; text-justify: inter-ideograph;">
<i><span style="color: blue; font-family: Arial; font-size: 11.0pt;">=> T<sub>left</sub> – T<sub>right</sub>
= 0 x a<o:p></o:p></span></i></div>
<div>
<!--[if !supportFootnotes]--><br clear="all" />
<hr align="left" size="1" width="33%" />
<!--[endif]-->
<div id="ftn1">
<div class="MsoFootnoteText" style="text-align: justify; text-justify: inter-ideograph;">
<a href="http://www.blogger.com/blogger.g?blogID=5641206422191665176#_ftnref1" name="_ftn1" title=""><span class="MsoFootnoteReference"><span style="font-family: Arial; font-size: 11.0pt;"><!--[if !supportFootnotes]--><span class="MsoFootnoteReference"><span style="font-size: 11pt;">[1]</span></span><!--[endif]--></span></span></a><span style="font-family: Arial; font-size: 11.0pt;"> Actually most of the forces we are
discussing in Mechanics are action-at-a-distance electromagnetic interactions.
We don’t observe this because we perceive only the macroscopic form of the
interaction which is the contact between objects.<o:p></o:p></span></div>
</div>
</div>
<!--EndFragment-->Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-72670281162861636642013-04-14T20:46:00.001+08:002013-04-15T08:42:26.576+08:00Typical problems in Newton's 2nd and 3rd Laws that are difficult for beginnersComplete the following questions for the 3 cases (see pictures)<br />
(a) Identify the forces acting on A and B separately even if they are interacting<br />
(b) Identify which pairs of forces that are a consequence of Newton' 3rd Law. <br />
(c) Calculate the magnitude and indicate the direction of all the forces on A and B separately<br />
(d) Calculate any forces on the rope if applicable<br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAUo7SXWToqUBMrydXdRQppXGBQKJZ59Kz1eQZDpF7ZiD60OMOxVSHOEABsGFfzu0ft-uPA5Ddn0z0UUahK2_5aW6W-7JkcfHqqWfy0FF2qS_sSbvssaMfqxofsHTUcx4Vgz7JEGYOZVKG/s640/blogger-image-952840069.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiAUo7SXWToqUBMrydXdRQppXGBQKJZ59Kz1eQZDpF7ZiD60OMOxVSHOEABsGFfzu0ft-uPA5Ddn0z0UUahK2_5aW6W-7JkcfHqqWfy0FF2qS_sSbvssaMfqxofsHTUcx4Vgz7JEGYOZVKG/s640/blogger-image-952840069.jpg" /></a></div>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-40038309616284937692013-04-14T14:39:00.000+08:002013-04-14T14:51:18.962+08:00Newton's 3rd Law - The difficulty from learner's perspective<br />
Below is a rather normal textbook example for Newton's 2nd Law:<br />
<br />
<div style="text-align: center;">
<i>A person pushes a box, mass xx kg on a frictionless surface with force yy N, determine the resultant force and acceleration of the box.</i></div>
<br />
Very few teachers will spend their time to discuss about the person pushing the box since identifying the forces on the box is sufficient to illustrate the use of <i>F = ma</i>. However if one is to take a closer look at the forces on the person pushing the box, there will be plenty of inconsistencies. This is the kind of textbook problems that plague physics teaching which are the source of confusion among students because it cannot exist in real life. There is no way the person standing on a frictionless floor to push the box for more than an instant! There is a contradiction between actual experience and physics principles. To deal with the discrepancy, students resorted to assimilate the solutions of this kind of problems through mental accommodation rather than through a consistent mental model. Many researches have pointed out that such laymen's preconceptions of how the world functions continue to persist in learners even after years of high quality science education.<br />
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<div class="p1">
What Newton's 3rd Law claims and how we perceive how forces work in the real world can be poles apart. To master it, learners have to stop relying on personal perceptions and use the laws which are unbias and self-consistent. Learners should start to build a consistent mental model from ground up rather than accomodate Newton's Laws with pre-existing perceptions. For the record, it took the ancients (from Aristotle to Newton's) almost 2000 years to realise that over-reliance on the senses lead to inconsistent scientific model. To master Newton's Laws of motion, we may want to take a leaf from a small part in a famous martial art novel <span class="s2">《</span><span class="s1">倚天屠龙记</span><span class="s2">》</span>.</div>
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<div class="separator" style="clear: both; text-align: center;">
<span class="s2" style="text-align: start;">《</span><span class="s1" style="text-align: start;">倚天屠龙记</span><span class="s2" style="text-align: start;">》</span><span class="s1" style="text-align: start;">里张三丰教张无忌太极拳里的片段</span></div>
<br />
Finally I appeal to all teachers and anxious parents to allow students the time to struggle with Newton's Laws. The more they struggle, the more they can distil the essence of the laws. Trying to shorten the 2000 years' of journey taken by scientists is not practical. If a teacher can teach the laws [in the textbooks] and the students can understand them with a few examples and assignments, why do we need teachers? We can easily replace teachers with DVDs of lectures and demonstrations (Hewitt or Walter Lewin just to name a few)!<br />
<br />
The following conversation may shed some light on the struggle of learners have in order to reconcile real world experience with Physics model.<br />
<br />
<div class="p1">
<i><span style="color: blue;"><b>Student</b> - If I am pushing a box on a frictionless surface, then the box should push back at me with the same amount of force. But if the box is moving in the direction i am pushing it, doesnt that mean that i am exerting a larger force on it?</span></i></div>
<div class="p1">
<i><span style="color: blue;"><br /></span></i></div>
<div class="p1">
<i><span style="color: blue;"><b>Teacher</b> - Why do you think you need a larger force to move the box in the direction of motion? Maybe you want to break down the question into the forces acting on the box and the man. Maybe sketch and drop me a pic?</span></i></div>
<div class="p1">
<i><span style="color: blue;"><br /></span></i></div>
<div class="p1">
<i><span style="color: blue;"><b>Student</b> - Because there needs to be a resultant force for the box to move? But if that's so then newtons third law doesn't apply... So it only applies for stationary objects?</span></i></div>
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<i><span style="color: blue;">student's sketch</span></i></div>
<div class="p1">
<i><span style="color: blue;"><br /></span></i></div>
<div class="p1">
<i><span style="color: blue;"><b>Teacher</b> - Newton's third law applies 100% of the time! Looking at what you have drawn, the box will accelerate to the right but the person will accelerate to the left! Do you think there is something missing on the person? Can you walk on a frictionless ground?</span></i></div>
<div class="p1">
<i><span style="color: blue;"><br /></span></i></div>
<div class="p1">
<i><span style="color: blue;"><b>Student</b> - Then the person should have a force by muscles letting him walk?</span></i></div>
<div class="p1">
<i><span style="color: blue;"><br /></span></i></div>
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<i><span style="color: blue;"><b>Teacher</b> - Nope. No one can walk on a frictionless floor! To walk, you need to be able to exert a force on the floor backward relative to you which gives rise to a force on you by the floor (see diagram). In fact you need to be able to exert a force by your legs larger than what you apply to the box in order for the situation to be possible in real life! Your question is the kind of textbook problems that plague physics teaching which led to confusion among students (You have brought up an excellent problem). If you look at the box alone, no problem, most students will be able to work out the acceleration of the box easily. However contradiction arises because the person can't accelerate forward with the box unless the floor under him miraculously turn into a rough floor for him to exert a force on it backward!</span></i></div>
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMTiKFZsro1II25nQ-dHvhUvimRCRgahNAo085P4H7qoswloji6FshyphenhyphenwslFSK_sYcX2ciLHvP2Ht_SnnYF5T-_lulQTWLFIXXrbKfzRebDEWwT8GNy5a38Q3gMRQFphr_I7HQnK7-yFgXR/s1600/IMG_6375.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><i><span style="color: blue;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiMTiKFZsro1II25nQ-dHvhUvimRCRgahNAo085P4H7qoswloji6FshyphenhyphenwslFSK_sYcX2ciLHvP2Ht_SnnYF5T-_lulQTWLFIXXrbKfzRebDEWwT8GNy5a38Q3gMRQFphr_I7HQnK7-yFgXR/s320/IMG_6375.jpg" width="265" /></span></i></a></div>
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<i><span style="color: blue;">Teacher's sketch</span></i></div>
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<i><span style="color: blue;"><b>Student</b> - But then if we use your first question of two boxes as an example, when box A pushes on box B, by N3L box B should push back with the same amount of force. But box B will move, which means its pushing back with less force. then how does N3L apply then? Or rather, why is there even resultant force in the world?</span></i></div>
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<i style="margin-left: 1em; margin-right: 1em;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjShKnDJVzYcbAhp_wwmrnMRjHs9Zh0PDBt2JaFkdRjbwaf4A40U8SOIJ6cjW6Pc2zn87E1kX7EH7jPCO-EyRRgTI2vH9LU5YKgUjB4JBmwOdDWzmhd3Q57p6ZhaVxEKo3MDkZ3Lfh-f_a8/s1600/IMG_6660.jpg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><span style="color: blue;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjShKnDJVzYcbAhp_wwmrnMRjHs9Zh0PDBt2JaFkdRjbwaf4A40U8SOIJ6cjW6Pc2zn87E1kX7EH7jPCO-EyRRgTI2vH9LU5YKgUjB4JBmwOdDWzmhd3Q57p6ZhaVxEKo3MDkZ3Lfh-f_a8/s320/IMG_6660.jpg" width="265" /></span></a></i></div>
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<i><span style="color: blue;">Question that is referred to by student</span></i></div>
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<i><span style="color: blue;"><b>Student</b> - Oh. Is it cause the amount of force with which B pushes back on A doesn't affect the resultant force of B itself cause it's on A, not B?</span></i></div>
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<i><span style="color: blue;"><b>Teacher</b> - Yes! Well done!</span></i></div>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-21950184964826821802013-04-03T20:57:00.001+08:002013-04-03T20:57:45.283+08:00Collision carts simulation for practical on 3/4/13Please complete the lab assignment P06 by 5/4/13.<br />
<br />
The simulation can be downloaded <b><span style="color: blue;"><a href="https://www.dropbox.com/s/v1igatsv5u7akit/ejs_Momentum1D2010web01.jar" target="_blank">here</a></span></b>.<br />
<br />
<i>Special thanks for <a href="http://weelookang.blogspot.sg/" target="_blank">Wee Loo Kang</a> for creating and refining this simulation with and for River Valley High School.</i>Unknownnoreply@blogger.com1tag:blogger.com,1999:blog-5641206422191665176.post-2038972307474199292013-04-03T20:51:00.000+08:002013-04-03T20:51:16.058+08:00What happens when you drop a spring balance with the measured object still on it?This video (shot at 120 frame-per-second) can be used to show that the spring balance does not measure the weight/gravitational force of the object hanging below rather it is measuring the force exerted by object.<br />
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<iframe allowfullscreen='allowfullscreen' webkitallowfullscreen='webkitallowfullscreen' mozallowfullscreen='mozallowfullscreen' width='320' height='266' src='https://www.youtube.com/embed/u5s6XCDUKIk?feature=player_embedded' frameborder='0'></iframe></div>
<br />
Concepts:<br />
<br />
<ul>
<li>The spring extends because the object exerts a force on the spring balance and the spring balance exerts an equal force on the object (Newton's 3rd Law). The force on the object exerted by the spring balance is equal to the gravitational force on the object when the system is in equilibrium (either at rest or at constant velocity). </li>
<li>When the system is accelerated (or free fall in this video), the force exerted on the spring balance by the object is different (zero at free fall) while the gravitational force on the object remains constant</li>
</ul>
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Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-20135962328217936522013-03-15T21:15:00.000+08:002013-04-03T21:19:17.336+08:00Performance of Understanding on Kinematics and Dynamics (15/3/2013)Stumble upon this through the Modelling Physics community in USA.<br />
<br />
<h3>
Using Direct Measurement Videos </h3>
<br />
"Direct Measurement videos show situations that students can use to learn and apply physics concepts. Grids, rulers, and frame-counters are added as overlays on the video. These allow students to make precise measurements of quantities such as position and time, without needing additional video analysis software." - <a href="http://serc.carleton.edu/sp/library/direct_measurement_video/index.html">http://serc.carleton.edu/sp/library/direct_measurement_video/index.html</a><br />
<br />
<h3>
Resources</h3>
<br />
<ul>
<li><a href="https://www.dropbox.com/s/xkbtkga4kyteonq/Performance%20of%20Understanding%20on%20Kinematics%20and%20Dynamics.pdf" target="_blank">Worksheet</a></li>
<li>Videos used in the worksheet - <a href="http://direct%20measurement%20video%20of%20people%20on%20collision%20carts/" target="_blank">video 1</a>, <a href="http://serc.carleton.edu/files/sp/library/direct_measurement_video/direct_measurement_video_blowd.mov" target="_blank">video 2</a>, <a href="http://serc.carleton.edu/files/sp/library/direct_measurement_video/direct_measurement_video_mampm.mov" target="_blank">video 3</a> and <a href="http://serc.carleton.edu/files/sp/library/direct_measurement_video/marble_collides_wood_block.v2.mov" target="_blank">video 4</a></li>
</ul>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-29043345271177230422013-02-06T12:00:00.000+08:002013-02-06T22:27:41.243+08:00Performance of Understanding - Kinematics (6-12/02/13)<h3>
Observing the phenomena</h3>
<div>
<ul>
<li><span style="background-color: white; font-family: inherit; white-space: pre-wrap;">Download the 2 videos on your iPad from dropbox </span><span style="background-color: white; font-family: inherit; white-space: pre-wrap;"> (Y3 LTL Class->Assignments->02 Kinematics->02 Assignments Video x.yyy)</span></li>
<li><span style="background-color: white; font-family: inherit; white-space: pre-wrap;">Observe the motion of the ball in each video. </span></li>
<li><span style="background-color: white; font-family: inherit; white-space: pre-wrap;">Post your ideas about the motion of the balls for the following questions <a href="https://docs.google.com/forms/d/1WSLnpfkt5ovcpyvk5xy3w2BzZkYCFJLP27KCVPYDJIY/viewform" target="_blank">HERE</a>.</span></li>
</ul>
<div>
<span style="white-space: pre-wrap;"><br /></span></div>
</div>
<h3>
Research the observed phenomena</h3>
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Conduct an in-depth study of the 2 motions of the balls using your knowledge of kinematic motion, graphs and equations.<br />
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Present your research findings using the <a href="https://www.dropbox.com/s/fom08my2sjzuuz3/lab%20report%20format.pdf" target="_blank">lab report format</a> (modified from modelling instruction course material 2007). A sample of a lab report (handwritten version) can be found <a href="https://www.dropbox.com/s/vhu5rv8wwqmrrm7/lab%20report%20sample.pdf" target="_blank">here</a>.</div>
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<h3>
Submission</h3>
<ul>
<li>You are advice to spend one and a half hour for this assignment.</li>
<li>iMessage me for clarification by 9/2/13.</li>
<li>Submit your report as a pdf (type written or neat handwriting using iOS app with any images collected) to me via email by 13/02/13 (Wed).</li>
</ul>
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<h3>
Technical Advices</h3>
<b><u>
Frame-by-Frame analysis using CoachMyVideo</u></b><br />
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In videos that we film for physics analysis, there is always a reference length (a metre rule, calibrated stick, etc) near to the object in motion. In the 2 videos, the distance between successive markings on the stick is 10 cm.</div>
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<ul>
<li>You can use your own ruler to measure the position of the object and make use of proportion to determine the position of the object from a reference point. </li>
<li>You may want to use adhesive tape, that is not too sticky, to secure your ruler to the iPad screen for ease of taking measurements.</li>
</ul>
<b><u>
iPad apps for collating lab report</u></b><br />
<ul>
<li><a href="https://itunes.apple.com/sg/app/penultimate/id354098826?mt=8" target="_blank">Penultimate</a> - handwritten notes with ability to attach images and sync with Penultimate</li>
<li>Evernote - typewritten report with image attachment. However difficult to write formulae</li>
<li>Neu.notes - similar to penultimate but is a paid app</li>
<li>Pages - microsoft equivalent for iOS devices. Very expensive!</li>
</ul>
Unknownnoreply@blogger.com0tag:blogger.com,1999:blog-5641206422191665176.post-42168307440015130202013-01-22T23:44:00.002+08:002013-01-23T15:56:12.522+08:00Motion of an Object II (Assignment)<p>1. Download the following video from Dropbox using your iPad (procedure to do that can be found <strong><span style="color: blue;"><a href="http://ltlphysics.blogspot.sg/2013/01/motion-of-object-assignment.html" target="_blank">here</a>)</span></strong></p>
<ul class="ul1"><li class="li1">Dropbox app -> "Y3 LTL Class" -> "Classroom activities" -> "02 Kinematics" -> "20130125 Motion of an object II"</li>
<li class="li1">Download "table tennis ball.mp4"</li>
</ul>
<div class="p1">2. Complete the following questions:<br>
<br>
<ul>
<li>Determine the ball's <strong>positions</strong>, <strong>distance from the starting point of the motion</strong>, <strong>clock reading </strong> and <strong>time interval from the start of the video</strong>. Record it in a table with the following column headings. (The centre of the ball begins its motion at the position of 2.7 cm when the clock reading is 0 s, each white line represent 10 cm interval on the metre rule)</li>
</ul><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjImQU8WEod4xopbidnzJ_ftH2_PxpZ2qlC5aNmRTbvmszLxBnOyrzZPw_XynB5t8UX4ADwPSHGtbpX2l7zztdSE-pZT5tgVsJqwoMYsTkzzwDeHeXaXP504Bdq0S0iZlnIfL6Cw4PenCcd/s1600/Screen+Shot+2013-01-22+at+10.46.36+PM.png" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjImQU8WEod4xopbidnzJ_ftH2_PxpZ2qlC5aNmRTbvmszLxBnOyrzZPw_XynB5t8UX4ADwPSHGtbpX2l7zztdSE-pZT5tgVsJqwoMYsTkzzwDeHeXaXP504Bdq0S0iZlnIfL6Cw4PenCcd/s400/Screen+Shot+2013-01-22+at+10.46.36+PM.png" id="blogsy-1358927746968.054" class="" alt="" width="400" height="27"></a></div>
<ul>
<li>Describe the motion of the ball qualitatively (i.e., with words)</li>
<li>Compare with the assignment you have just completed (refer to <a href="http://ltlphysics.blogspot.sg/2013/01/motion-of-object-assignment.html" target="_blank"><strong><span style="color: blue;">here</span></strong></a>), state the difference(s) between the motion of the table tennis ball and the toy cars.</li>
<li>Create a possible motion map of the table tennis ball.</li>
<li>Use Graphical Analysis app to determine the linearised relation between the distance from starting point (y-axis) and time interval (x-axis). </li>
</ul>
<p>3. Find a way to put all your work above in a single document (I would suggest Evernote or some handwriting app that you can insert pictures). This is in anticipation of future larger projects and experiment. </p>
</div><div class="p1"><span style="color: red;"><br>
</span><span style="color: red;"><strong>Hint to complete the assignment using CoachMyVideo app</strong></span><br>
<span style="color: red;">Do you need to capture the positions of the ball at equal position intervals?</span></div>
<p> </p>Unknownnoreply@blogger.com0