1. Momentum

2. What is Momentum?
Momentum – tendency of objects to keep going in the same direction with the same speed
Depends on mass and velocity
Has direction

3. The momentum of a ball depends on its mass and velocity
Ball B has more momentum than ball A

4. The momentum of a ball depends on direction too

5. Which has greater momentum: a train at rest or a moving skateboard?
Question
Which has greater momentum: a train at rest or a moving skateboard?
The moving skateboard has a greater momentum because it has a velocity. The train at rest has a greater mass, but zero velocity.

6. Conservation of Momentum
Conservation of Momentum – momentum cannot be created or destroyed, only transferred
p before = p after
VIDEO

7. Collisions Collision – occurs when two or more objects hit each other
During a collision, momentum is transferred from one object to another because Momentum is conserved.

8. Collisions Elastic Collision – objects bounce off each other
Inelastic Collision – objects stick to each other

9. Practice
A 1200 kg car drives west at 25 m/s for 3 hours. What is the car’s momentum?
(1200 kg) × (25 m/s) = 30,000 [kg m/s] west

10. Practice (1300 kg) × (13.5 m/s) = 17,550 kg m/s north Motorcycle
A car is traveling at a velocity of 13.5 m/s north on a straight road. The mass of the car is 1,300 kg. A motorcycle passes the car at a speed of 30 m/s. The motorcycle (with rider) has a mass of 350 kg. Calculate and compare the momentum of the car and motorcycle.
Car
(1300 kg) × (13.5 m/s) = 17,550 kg m/s north
Motorcycle
(350 kg) × (30 m/s) = 10,500 kg m/s north

11. Practice (15 kg m/s) ÷ (30 m/s) = .5 kg
A ball moving at 30 m/s has a momentum of 15 kg m/s. What is the mass of the ball?
(15 kg m/s) ÷ (30 m/s) = .5 kg

12. PRACTICE
A 700 Kg boat moves with the momentum of 120,000 kg*m/s, what is the velocity of the boat?
v=p/m v=120,000 kg*m/s /700 kg
v= m/s

13. PRACTICE A 150 kg astronaut in space throws a
5 kg wrench at a speed of 15 m/s, which best describes her velocity?
Greater than 15 m/s same direction to wrench
Less than 15 m/s opposite direction to wrench
Greater than 15 m/s opposite to wrench D.

14. PRACTICE
A 6 kg ball is moving at 6 m/s to the right and a 8 kg ball is moving at 5 m/s to the left. What is the total momentum of the system? (6kg)(6m/s)=36kg*m/s right (8kg)(5m/s)=40kg*m/s left System momentum=4kg*m/s left