4/1/09
Post date: Mar 31, 2009 12:2:4 AM
Bell Ringer: Use the impulse momentum theorem to explain how airbags help protect us in a car crash.
Time for questions, finish labs if needed
Review impulse-momentum equation and implications
If we're changing speeds (say, from a high speed to a stop) our change in momentum will be the same no matter what force or time is used to accomplish that.
Very high forces can be hazardous to our health!
These high forces occur when the time is very small. Many safety devices (especially in cars) aim to spread a stopping force over a longer period of time.
Air bags
Crumpling bumpers
Parachutes - remember, it's not the fall that kills you, it's the sudden stop at the end!
Spiderman and momentum video: http://www.youtube.com/watch?v=kuVpwjYgvgg
Neo catching Trinity - does more harm than good!
Conservation of Momentum
Newton's third law implies that in a collision, the total momentum will remain constant for a closed system
p initial = p final
Page 185: 5-8 due Thursday