In Demo Veritas

Hey, where did the categories go?

Must have been the upgrade to wordpress.  I liked the categories, I guess I will put them back in.  I can go over my ouevre and re-assign.  I haven’t hit 100 posts yet, so its not that laborious.

Physics demos today.

A rigid pair of verticals and a horizontal clamped up to make a suspension for a 1.00 m pendulum, with a 30 mm brass ball as the bob.  The bob can move in two directions, making it a circular pendulum.

A 65# wrecking ball is suspended from the ceiling skyhook with wire rope.  The physics victim takes hold of the ball, and walks backwards to the blackboard, drawing the ball up to his chin.  With head against the blackboard, the victim releases the ball.  It swings out as a pendulum, and then swings back in.  Conservation of momentum predicts the wrecking ball will not hit the chin.  The owner of the chin can be forgiven for flinching.  The ball returns to within a centimeter of its release point.  It is a viscerally impressive lesson in physics.

How much equipment does it take to measure little g, by dropping an apple from the ceiling of the lecture hall?  A lot.  I’ll post photos on Thursday when we do it again for another physics class.