2. What is momentum? We say the Packers have momentum entering the final weeks of the season… Anything that is moving has momentum

3. Momentum is what Newton called the “quantity of motion” of an object.

4. Momentum describes the tendency of moving objects to keep going in the same direction with the same speed. It is a property of moving matter only. Changes in momentum create forces or can result from forces. The momentum of an object: Depends on the object’s mass. It is directly proportional to mass. Depends on the object’s velocity. It is directly proportional to velocity.

5. The momentum of a moving object is its mass multiplied by its velocity. That means momentum increases with both mass and velocity. Momentum (kgm/sec) Velocity (m/s) Mass (kg) p = m v

6. In symbols: p = mv or p m v

7. Which has more momentum, a supertanker tied to a dock or a raindrop falling? p = mv Supertanker: 0 m/s Raindrop: 0.5 m/s Anything times 0 is 0, so supertanker has 0 momentum, while the raindrop has some!

8. Momentum describes the tendency of objects to keep going in the same direction at the same speed. Changes in momentum result from forces or create forces. Both balls are 1 kg, but B is moving faster.

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

10. 1 kg Ball A is moving 1m/s, 1 kg Ball B at 3 m/s. A 1 N force is applied to deflect the motion of each ball. What happens? Does the force deflect both balls equally? A B ?

11. Ball B deflects much less than Ball A when the same force is applied because Ball B had a greater initial momentum.

12. A car is traveling at a velocity of 13.5 m/sec (30 mph) 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/sec (67 mph). The motorcycle (with rider) has a mass of 350 kg. Calculate and compare the momentum of the car and motorcycle Use: p = m v Solve for car: p = (1,300 kg) (13.5 m/s) = 17,550 kg m/s Solve for cycle: p = (350 kg) (30 m/s) = 10,500 kg m/s The car has more momentum even though it is going much slower because it’s more massive.

13. The total momentum of two objects before a collision is equal to the total momentum of the two objects after the collision.

14. If no external forces act on a system, the total momentum of the system will not change. Such a system is called an isolated system. Momentum is conserved in every isolated system. In practice, for any event in an isolated system: Momentum after = Momentum before

15. The law of conservation of momentum states when a system of interacting objects is not influenced by outside forces (like friction), the total momentum of the system cannot change. If you throw a rock forward from a skateboard, you will move backward in response.

16. When two or more objects interact (collide) the total momentum before the collision is equal to the total momentum after the collision

17. A collision occurs when two or more objects hit each other. During a collision, momentum is transferred from one object to another. Collisions can be elastic or inelastic.

19. During this collision the speed of the red car is transferred to the blue car. The total momentum remains constant before & after the collision. The masses of both cars are the same so the velocity of the red car is transferred to the blue car.

20. During this collision the speed of both box cars changes. The total momentum remains constant before & after the collision. The masses of both cars is the same so the velocity of the red car is transferred to the blue car.

21. Inelastic collisions m A v A1 + m B1 v B1 = m A v A2 + m B v B2

22. Two 0.165 kg billiard balls roll toward each other and collide head-on. Initially, the 5-ball has a velocity of 0.5 m/s. The 10-ball has an initial velocity of -0.7 m/s. The collision is elastic and the 10-ball rebounds with a velocity of 0.4 m/s, reversing its direction. What is the velocity of the 5-ball after the collision?

23. You are given mass, initial velocities, & the 5-ball’s final velocity. Diagram the motion, use m 1 v 1 + m 2 v 2 = m 1 v 3 + m 2 v 4 Solve for V 3 : (0.165 kg)(0.5 m/s) + (0.165 kg) (-0.7 kg)= (0.165 kg) v 3 + (0.165 kg) (0.4 m/s) V 3 = -0.6 m/s

24. After this collision, the coupled cars make one object w/a total mass of 60,000 kg. Since the momentum after the collision must equal the momentum before, the velocity must change. In this case the velocity is reduced from 10 m/sec. to 5 m/sec.

25. Momentum changes when a net force is applied. The inverse is also true: If momentum changes, forces are created. If momentum changes quickly, large forces are involved. (SEATBELTS!!!!!)

26. The relationship between force and motion follows directly from Newton's second law.

27. Inertia is another property of mass that resists changes in velocity; however, inertia depends only on mass. Inertia is a scalar quantity. Momentum is a property of a moving mass that resists changes in its velocity. Momentum is a vector quantity.

28. Kinetic energy and momentum are different quantities, even though both depend on mass and speed. Kinetic energy is a scalar quantity. Momentum is a vector, so it always depends on direction. Two balls with the same mass and speed have the same kinetic energy but opposite momentum.

29. Nearly all modern airplanes use jet propulsion to fly. Jet engines and rockets work because of conservation of linear momentum. A rocket engine uses the same principles as a jet, except that in space, there is no oxygen. Most rockets have to carry so much oxygen and fuel that the payload of people or satellites is usually less than 5 percent of the total mass of the rocket at launch.