Daily Archives: April 4, 2012

3.30.12

Today’s meeting was specially hosted by Cedric Flamant, past SciClub VP (yay!). First, however, Marcus demonstrated how a magnet dropped through a metal tube falls slower than it would in free fall. This is because the movement of the magnet induces a current in the tube, which then generates a magnetic field that counters the magnet’s fall in a process encapsulated by Lenz’s Law.

Next, Cedric talked about hats. If you just want to slide a hat along a table, it’s easier when it’s right-side up, but if you want to spin it, you should actually have it upside down because the torque required will be less (torque is a measure of how hard you have to push to rotate something, and it’s equivalent to the cross product of the radius from the center of mass and the force).

Cedric also did some magic physics with a battery, a screw sticking out of the bottom of the battery, a magnet on the bottom of the screw, and a wire connecting the top of the battery to the magnet. As the current through the wire passes through the magnetic field from the magnet, the Lorentz force creates a torque that causes the screw and magnet to spin. He attached LEDs to them to make the spinning more obvious.