tag:techtv.mit.edu,:Array/231729720 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/231708800 2007-12-27 14:44:35 -0500 Doc Edgerton Films Watch a film about Synchronous Motor Motional Transients in this silent film by Doc Edgerton. 184 tag:techtv.mit.edu,:Array/231687880 2009-06-01 15:48:40 -0400 MIT Department of Physics Technical Services Group Two or more air carts are connected by springs on an air track. When this system is at resonant frequency, symmetrical patterns called <a href="http://en.wikipedia.org/wiki/Normal_mode">normal modes</a> appear. The normal modes are shown in both undriven and driven cases. In the undriven examples, the normal modes are found by placing the carts at certain distances from each other and then letting them oscillate. In the driven examples they are found by driving the system with a motor, and varying the frequency until the normal mode patterns appear. Both of these methods are shown for systems of two, three, and five coupled carts. 459 tag:techtv.mit.edu,:Array/231668980 2009-07-07 11:45:24 -0400 MIT Department of Physics Technical Services Group A long beaded chain is looped over a motor pulley. When the motor is turned on, a disturbance in the chain causes waves to propagate through it. When the motor is brought up to full speed and the chain is knocked off the pulley it will maintain its shape for a few seconds and appear to "walk". 87