tag:techtv.mit.edu,:Array/226007380 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/225986480 2008-06-06 11:36:25 -0400 MIT Department of Physics Technical Services Group An RF transmitter is connected to a long antenna, emitting radio waves. A dipole antenna with a light bulb between its elements acts as the receiver. When the receiving antenna is parallel to the transmitter, the radio waves are absorbed, creating a current in the antenna and causing the bulb to glow. When perpendicular, no current is created, and the bulb does not glow. 57 tag:techtv.mit.edu,:Array/225967480 2008-06-20 16:53:07 -0400 MIT Department of Physics Technical Services Group <p>A light bulb is placed in series with two copper plates immersed in de-ionized water. Touching the plates closes the circuit, lighting the bulb.</p><p>When kosher salt is dropped into the de-ionized water, the salt dissolves, causing ions to be dispersed throughout the liquid. The free ions allow current to flow through the water, which completes the circuit and lights the bulb.</p><p>Most water we encounter in everyday life is not de-ionized and contains impurities with dissolved ions. This is why we know water as a good conductor, and why we shouldn't use electronic devices around a bathtub, for example.</p> 54 tag:techtv.mit.edu,:Array/225948520 2009-06-03 15:26:02 -0400 MIT Department of Physics Technical Services Group Odd-shaped objects with their centers of mass marked by orange paint are thrown. While the objects appear to follow very wobbly trajectories when viewed under bright lights, under black lights you can see that their centers of mass travel in smooth parabolas. <br><br> Then center of mass is not necessarily in the center of an object, as demonstrated by the last object in the video (a weighted disk). 91 tag:techtv.mit.edu,:Array/225929560 2009-06-10 14:04:53 -0400 MIT Department of Physics Technical Services Group Two pucks of the same mass are slid at each other on an air table, and their resulting collisions demonstrate conservation of momentum. Notice on the first collision, for example, that when a moving puck hits a stationary puck dead-on, that the second puck leaves with the same velocity as the first, and the first puck stops moving completely. 80