tag:techtv.mit.edu,:Array/218628960 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/218550940 2008-06-20 15:47:45 -0400 MIT Department of Physics Technical Services Group <p>A small glass tube, held by copper wire, is placed in series with a light bulb. The glass acts as an insulator at room temperature, meaning the current cannot flow between the copper wires. This leaves an open circuit and the light bulb does not light up. Touching a conductor across the copper wires (with a metal screwdriver for instance) does complete the circuit because it allows current to flow.</p><p>However, when glass is sufficiently heated by a torch it becomes an ionic conductor. Ionic bonds in the glass are broken, allowing the charge carrying ions to move freely. Thus, when the glass is melted the current can flow, which closes the circuit and lights the bulb. </p> 72 tag:techtv.mit.edu,:Array/218483720 2009-01-08 13:12:55 -0500 6.370 BattleCode MIT Programming Competition BattleCode 2009: Part 1 - Intro 1988 tag:techtv.mit.edu,:Array/218459140 2009-01-21 14:43:14 -0500 MIT Department of Physics Technical Services Group A light bulb is connected in series with a coil of very fine copper wire and a DC power supply. The voltage is adjusted so that the bulb glows dimly. When the coil is immersed in liquid nitrogen the resistance of the wire decreases causing the current to increase and the bulb to glow brightly. 71