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. Question Which has greater momentum: a train at rest or a moving skateboard?

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 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 A child is on a sled moving down a hill at 20 m/s. The combined mass of the sled and child is 100 kg. What is the momentum of the child and sled? (100 kg) × (20 m/s) = 2,000 kg m/s downhill

12. Practice 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

13. Practice A boat is sitting at rest a short distance from a dock. A child in the boat throws a 6.4 [kg] package out horizontally with a speed of 10 [m/s] towards the dock. Calculate the total momentum of the system after the package is thrown. p (before) = (26 [kg] + 45 [kg] + 6.4 [kg]) * 0 [m/s] = 0 [kg*m/s] So, p (after) = 0 [kg*m/s] The total momentum after the package is thrown is the SAME as before it was thrown. WHY?