We have used white and orange ping pong balls. The walls are mostly various "academic cinder block off-whites," but in one case a darker gray and another a darkly stained wood door. We have not tried to shine a light across the ball's path. It would take less than a millisecond for the ball...
Water is diamagnetic and is weakly repelled by a strong magnet. The effect is very small but can be observed with a shallow dish of water and a very strong magnet. Humans are mostly water. A number of other materials are diamagnetic as well. A vibrating feeling could be present if there are...
We have a ping pong ball cannon which shoots the ball at just under the speed of sound. In a classroom setting you cannot see the ping pong ball between the time the cannon is fired and when the ball hits the wall several meters away. On the other hand, that speed is not that much different...
A figure 8 coil can be effective at reducing pick-up from time-dependent, but spatially uniform, magnetic fields. However, the time-dependent magnetic fields from an MRI machine are not uniform magnetic fields. An MRI machine uses a large constant field, which will not contribute directly to...