Tuesday, November 25, 2008 - Blocks 1 and 3

Collected RA 5.2

Went around the room and asked what they learned from yesterday's class.

Handed back and quickly went over RA 5.1
Demo with blowpipes and marshmallows to show that longer cannons impart more impulse (same force, longer time) than short cannons.

Skare's demo with happy and sad balls knocking down block.

Conservation of momentum: If there is no net external force acting on a system then there is no change in momentum of the system.
It does not apply in all cases (such as falling object as system) but it has never been shown to fail.

Applied Conservation of Momentum to collisions:
Two basic types of collisions
1. Inelastic collisions: things stick
2. Elastic collisions: things bounce
If there is no net external force, momentum is conserved in both types of collisions.

Worked problem of inelastic collision on board.

Demo of inelastic and elastic collisions with air track.

Handed out Inelastic Collisions worksheet. Students worked on it in class and handed it in.
Handed out CD chpt 5 due for the last time next Wed. It asks for pictures, if you don't draw them then I will return the paper.
Handed out RA 5.3 due tomorrow.