1. Momentum

2. Momentum
Momentum is a property of moving objects

4. Impulse & Momentum
A force acting over a given time (an impulse) can change an object’s momentum
Example:  If the wall exerts a force of 10,000 N and the contact time is 0.01 s. What is the impulse? What is the change in momentum? I = Impulse = F t  = 100 Ns
change in momentum = impulse = 100 Ns

5. Impulse and Contact Time

6. Conservation of Momentum
You may wish to discuss the examples given in the text on p. 79
The total momentum of a system can’t change unless an external force is applied
Interacting objects exchange momentum through equal and opposite forces

7. Spinning or orbiting objects have angular momentum
Angular momentum = mass x velocity x radius L = m v r

8. This explains why objects rotate faster as they shrink in radius:
Conservation of (angular) momentum: the angular momentum of an object can’t change unless an external twisting force is applied
This explains why objects rotate faster as they shrink in radius:
Discuss astronomical analogs: disks of galaxies, disks in which planets form, accretion disks…
m x v x R = m x V x r

9.
For an orbiting body, this means if r is small, v is big and if r is big, v is small