1. MOMENTUM

2. 8.1 Momentum
A truck rolling down a hill has more momentum than a roller skate with the same speed. But if the truck is at rest and the roller skate moves, then the skate has more momentum. Moving objects can have a large momentum if it has a large mass, a high speed or both.
They have the same momemenutm if the speed of the roller skate is much greater than the speed of the truck.
Can you think of a case when this truck and roller skate would have the same momentum?

3. Sample Problem 1
Which has more momentum? A pick up truck traveling at 60 mph or a pick up truck traveling at 100 mph?
Which has more momentum? A pick up truck or a smart car? Why?

4. Practice Problem #2
An ostrich with a mass of 146kg is running to the right with a velocity of 17m/s. Find the momentum of the ostrich.

5. IMPULSE

6. Which one would you prefer to hit? A hay stack or a concrete wall?

7. MOMENTUM IMPULSE
Combining the two

8. Sample Problem 3
A 1400kg car is travelling westward at a velocity of 15m/s, when it veers off the road and collides with a pole and is brought to rest in 0.30s. How much force is exerted on the car during the collision?

9. 4. Although it cannot sustain its top speed for more than 8
4. Although it cannot sustain its top speed for more than 8.65 s, the cheetah can run a distance of 274 m during that time. If a cheetah with a mass of 50.0 kg is moving north at its top speed, what is its momentum? First find velocity.

10. Summary
Physics of Car Crashes
hewitt drew it

11. And now we have an answer to our the question we started with today…
Why is it important to “follow through”…
If you want to increase the momentum of an object you have to apply the greatest force possible for as long as possible.
Swinging as hard as possible for as long as possible will give the ball the most momentum.

13. Khan Academy Tutorial

14. 8.2 Impulse Changes Momentum
If momentum changes then either the mass, velocity or both have changed. In most cases the velocity changes. And we learned from previous units if you have a change in velocity then the object is ACCELERATING
We know that ACCELERATIONS are produced by FORCES.
So the greater the FORCE on an object, the greater its ACCELERATION so the greater its change in velocity and therefore the greater its change in MOMENTUM.

15. Stopping Time and Distance
The amount of stopping time for a vehicle, as well as its stopping distance, is governed by the impulse-momentum theorem.
A truck with a heavy load will take longer to stop than the same truck without a load.

16. 8.2 Impulse Changes Momentum
When hitting either the wall or the haystack and coming to a stop, the momentum is decreased by the same impulse.
The same impulse does not mean the same amount of force or the same amount of time.
It means the same product of force and time.
To keep the force small, we extend the time.