Wednesday, Dec 10, 2008 - Blocks 1 and 3

Handed back and went over RA 6.1, RA 6.2

Wrote energy balance for pushing on block with friction and solved for final velocity. Solved the equation using acceleration to get the same answer.

Showed technique of inserting the coefficient into the KE or PE terms to calculate the new KE or new PE. Very powerful and useful technique. (Ex. What happens to the stopping distance of a car if you double the speed and double the mass?
KE old = 1/2 * m*v^2
KE new = 1/2 (2m) * (2v)^2 = 8 * 1/2 * m * v^2

Brought out swinging ball device and showed that situations that still obey conservation of momentum do not happen because they do not conserve energy.

Went over several energy balance equation situations.
Two balls coming together and stopping in inelastic collision. (Used steel balls to show energy is converted into heat that burns a hole through the paper.)
Roller Coaster Lab.
Car going up hill with friction.
Dropping a ball with no air resistance. How fast?
Looney Tunes Lab: At bottom, at half-way point, at 3/4 point down

Handed out RA 6.3 (due Friday)
Handed out CD 6.1, CD 6.2 due for last time next Wednesday.
Test on energy on Thursday of next week.
Friday: Physics poems and songs. Write an original poem or song and present it to the class.