tag:techtv.mit.edu,:Array/218872700 2008-10-10 14:24:44 -0400 MIT Department of Physics Technical Services Group Two carts are connected together on an air track with a spring. Under bright lights you can see the coupled oscillation of the carts back and forth, but under black lights you can see that the center of mass moves at a constant velocity. 103 tag:techtv.mit.edu,:Array/218848000 2008-08-28 14:21:12 -0400 MIT Department of Physics Technical Services Group <p>A wooden ball is attached to the rim of a spinning wheel. The ball is held in place by a string. When the spring is cut, the ball flies in a straight tangent to the wheel.</p><p>In the camera's frame of reference, the ball constantly accelerates around in a circle due to the centripetal force pulling it inwards. When the string is cut, the acceleration stops, and the ball flies away in a straight tangential line. When the string is cut in the rotating frame of reference, a ficticious force (centrifugal force) accelerates the ball. </p> 79 tag:techtv.mit.edu,:Array/218827500 2008-10-21 11:04:51 -0400 MIT Department of Physics Technical Services Group A CO2 fire extinguisher is mounted on the back of a tricycle. When the CO2 is released, the tricycle is propelled forward. Watch Professor Lewin perform this demonstration on the Martha Stewart Show: <a href="http://www.marthastewart.com/show/the-martha-stewart-show/teacher-appreciation-day?lnc=4ef2dc5bfca40110VgnVCM1000003d370a0aRCRD&amp;rsc=showarchive_tv_show-archive">http://www.marthastewart.com/show/the-martha-stewart-show/teacher-appreciation-day?lnc=4ef2dc5bfca40110VgnVCM1000003d370a0aRCRD&amp;rsc=showarchive_tv_show-archive </a> 53 tag:techtv.mit.edu,:Array/218805520 2009-01-06 13:23:42 -0500 MIT Department of Physics Technical Services Group A plexiglass rod rubbed with fur picks up a positive electric charge, while a rubber rod rubbed with fur picks up a negative electric charge. When either rod is brought in contact with hanging tinsel, the tinsel becomes charged and flares out. The other rod, however, will now attract the tinsel. Touching the tinsel with your hand discharges it. <br> <br> These electrostatic forces can also be seen with a conducting balloon. Touching a charged rod to the balloon transfers charge, causing the balloon to be repelled away from the rod. <br> <br> The ancient Greeks noticed this phenomenon when rubbing pieces of amber (which pick up a negative electric charge, like our rubber rod). The word "electricity" is based on the Greek name for amber: "elektron." 123 tag:techtv.mit.edu,:Array/218779920 2009-06-11 14:02:02 -0400 MIT Department of Physics Technical Services Group An air puck is attached to a string that passes through the center of an air table. A weight is attached to the end of the string. The ball is set into rotation in a horizontal circle. When the weight is released, creating a constant force inwards, the radius of the path is shortened and the puck speeds up. A similar effect is seen when the string wraps around a center rod like a tether ball. This creates an increasing force, which causes the puck to inspiral more quickly. 181