tag:techtv.mit.edu,:Array/223217900 2007-05-13 11:42:51 -0400 revrev a short experiment in high definition video and surround sound (neither of which are possible on this site). nevertheless, the imagery is pertinent, and attempts to document a fall day at mit. music by mike fabio.<br /> 331 tag:techtv.mit.edu,:Array/223197320 2008-07-18 11:31:42 -0400 MIT Department of Physics Technical Services Group <p>A 100 uF oil-filled capacitor is charged to 3 KV. This takes approximately 15 minutes, creating a charge on the capacitor that could be lethal. The capacitor is then discharged through a 12" length of 30 gauge bare iron wire.</p><p>When the high voltage current flows though high resistance wire, the bonds between iron molecules are shattered, resulting in a loud bang, a shower of sparks, and a cascade of wispy filaments floating through the air.</p><p>Not all of the charge on the capacitor is disharged through the wire, so a shorting bar must be used to release the remaining charge. </p> 121 tag:techtv.mit.edu,:Array/223172980 2008-09-02 10:20:19 -0400 MIT Department of Physics Technical Services Group <p>A stuffed monkey is suspended from a rod at one end of a lecture hall by an electromagnet. A golf ball gun aimed directly at the monkey cuts power to the electromagnet when fired. Thus, the monkey begins falling at the same instant the gun fires the golf ball. The projectile and target meet in mid air.</p><p>Intuitively one might think that the ball will go over the monkey's head due to its fast speed. However, gravity accelerates all objects downward at the same rate, meaning the monkey and the ball will meet at exactly the same point. If the ball was shot even faster, it would still hit the monkey, but higher above the ground. </p><p>No animals were harmed in this demo. </p> 77 tag:techtv.mit.edu,:Array/223152620 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/223133320 2008-09-02 15:08:22 -0400 MIT Department of Physics Technical Services Group A pair of spinning wheels 1.5 meters apart is placed in the path of a bullet. A bullet is fired with the wheels stationary for reference position, and fired again with the wheels spinning at a known speed. The second wheel will rotate more than the first as the bullet crosses the gap between them. When the angles between the reference holes and the second holes are compared, the speed of the bullet can be determined. <br><br> The balloon is used to show when the bullet has passed through both disks. <br><br> This video was shot with a Phantom v7.1 high speed video camera (donated by Vision Research Inc.) at approximately 7000 frames per second. The frame data can be seen at the bottom of the screen. <br><br> Special thanks to Dr. Jim Bales, MIT Edgerton Center. 22 tag:techtv.mit.edu,:Array/223114140 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