1. Conservation of Momentum
CHAPTER 12 – MOTION AND MOMENTUM
Conservation of Momentum

2. Conservation of Momentum pg 339
1. What is the law of conservation of momentum?
The total momentum of objects that collide with each other does not change

3. Conservation of Momentum pg 339
2. What outside forces could impact a collision?
friction
gravity
3. Why “might” these forces be ignored?
sometimes the effects of these forces are small enough to be ignored

4. Conservation of Momentum pg 339
4. What are some ways collisions occur?
bouncing off ex: bowling balls and bowling pins sticking together ex: football players during a tackle
after colliding, objects still move stuck together, but at different speeds
5. Sticking together

5. Conservation of Momentum pg 340
mass of bag: 2 kg
step 1: what do you know?
6. Find total momentum if a 2 kg backpack is tossed at a speed of 5 m/s to a person at rest with a mass of 48 kg.
speed of bag: 5 m/s
mass of person: 48 kg
speed of person: 0 m/s
step 2: what do you want to find?
total momentum
= bag’s momentum
+ person’s momentum
step 3:
substitute
total momentum
= 2 kg * 5 m/s
+ 48 kg * 0 m/s
= 10 kg * m/s

6. Conservation of Momentum pg 340
mass of bag: 2 kg
step 1: what do you know?
speed of bag: 5 m/s
7. Find the final velocity of the person and the backpack from #6.
mass of person: 48 kg
speed of person: 0 m/s
total momentum:
10 kg * m/s
step 2: what do you want to find?
final velocity
momentum: p = m * v
v = p/m
step 3:
substitute
v = 10 kg * m/s
50 kg
= 0.2 m/s

7. Conservation of Momentum pg 342
after colliding, two objects bounce off each other, but they may transfer momentum from one to another
8. Bouncing
off
total momentum is the same before and after the collision
9. Total momentum