1. Bellringer 9/30
A skier leaves the horizontal end of a ramp with a velocity of 25.0m/s East and lands 70.0 m from the base of the ramp. How high is the end of the ramp from the ground?

2. Chapter 6: Momentum and Collisions

3. Momentum = mass x velocity
Momentum – the product of the mass and velocity of an object
Vector quantity – direction matches the velocity
Linear Momentum (p):
p=mv
Momentum = mass x velocity
SI units: kg●m/s

4. Momentum

5. Momentum
If both of these objects are moving down the street at the same speed… which has the greater momentum?
What about if the Mack truck is at rest… what object has the greatest momentum?

6. Roll Tide!!

7. Practice Problems
A 2250 kg pick up truck has a velocity of 25 m/s to the east. What is the momentum of the truck?
p = 5.6x104 kg●m/s to the east

8. Practice
A 21 kg child on a 5.9 kg bike is riding with a velocity of 4.5 m/s to the northwest.
What is the total momentum of the child and the bike together?
What is the momentum of the child?
What is the momentum of the bike?

9. Impulse-Momentum Theorem
Impulse = product of the force and the time over which the force acts on an object
Impulse-Momentum Theoren
FΔt= Δp or F Δt= Δp=mvf -mvi
Force x time interval = change in momentum

10. Practice
A 1400 kg car moving westward with a velocity of 15m/s collides with a utility pole and is brought to rest in 0.30s. Find the force exerted on the car during the collision.
F = 7.0 x 104 N to the east

11. Stopping Distance
Stopping times and distance depend on impulse momentum theorem
Force is reduced when the time interval of impact is increased

12. Stopping Time
F t = F t
Imagine a car hitting a wall and coming to rest. The force on the car due to the wall is large (big F ), but that force only acts for a small amount of time (little t ). Now imagine the same car moving at the same speed but this time hitting a giant haystack and coming to rest. The force on the car is much smaller now (little F ), but it acts for a much longer time (big t ). In each case the impulse involved is the same since the change in momentum of the car is the same. Any net force, no matter how small, can bring an object to rest if it has enough time. A pole vaulter can fall from a great height without getting hurt because the mat applies a smaller force over a longer period of time than the ground alone would.

14. Practice
A 2240 kg car traveling west slows down uniformly from 20.0m/s to 5.00m/s. How long does it take the car to decelerate if the force on the car is 8410 N to the east? How far does the car travel during the deceleration?

15. Impulse-Momentum Theorem