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Momentum

Formula: Unit:

Direction: Type:

Mass:

Inertia:

Kinetic energy:

Momentum:

Kinetic energy

Momentum

Inertia

2. Compare the inertia, momentum, and kinetic energy of a 100. kg football player running at 2.0 m/s and a 50. kg field hockey player running at 3.0 m/s.

Compare the quantities listed below for each pair of objects.

1. What is the momentum of a 1500 kg car traveling east at 20. m/s?

|Inertia | | |

|Momentum | | |

|Kinetic Energy | | |

|Inertia | | |

|Momentum | | |

|Kinetic Energy | | |

|Inertia | | |

|Momentum | | |

|Kinetic Energy | | |

How does an object gain or lose momentum? What determines how much momentum it gains or loses?

Formula: Unit:

Type:

Impulse

1.

2.

1. A 50. kg runner accelerates from 2.0 m/s to 3.0 m/s. What is her:

a) initial momentum?

b) final momentum?

c) change in momentum?

d) What impulse did she apply?

4. A player kicks a 0.50 kg football and the force versus time graph is shown at right.

a) What impulse does he apply to the ball?

b) How much does the momentum of the ball change as a result?

c) How fast is the football going after the kickoff?

8. Compare the impulse when a 1.0 kg ball bounces off the floor to when it doesn’t.

7. Compare the impact force, contact time, impulse, acceleration, and change in momentum for each vehicle in the impending collision.

5. Why are airbags used in cars? What are some other safety devices that operate on the same principle?

5. A 1500. kg car is in contact with a wall for 0.15 seconds. Calculate:

7. Which cannon will shoot the cannonball further? Why?

In general,

6. Why do coaches always tell you to “follow through” on the ball?

Notice that the force

a)

b)

3. How can an impulse be determined from a force-time graph?

a) its change in momentum

b) the impact force

Impact Force

4. If your brakes fail in your car, would you rather drive into a brick wall or a haystack? Why?

6. What are some other examples of this principle?

2. A player kicks a 0.50 kg soccer ball with an average force of 10. N. His foot is in contact with the ball for 0.40 s.

a) What impulse does he apply to the ball?

b) How much does the momentum of the ball change as a result?

c) What is the final velocity of the soccer ball?

Conservation of Momentum

Principle of Conservation of Momentum

Isolated system:

Meaning of principle:

Formula:

1).

2)

3)

Explosion

Sticky Collision

Bouncy Collision

Momentum is conserved in each direction.

4)

1. A 1850 kg luxury sedan stopped at a traffic light is struck from the rear by a compact car with a mass of 975 kg. The two cars become entangled as a result of the collision. If the compact car was moving at a velocity of 22.0 m/s to the north before the collision, what is the velocity of the entangled mass after the collision?

3. Two dynamics carts at rest are pushed apart by a compressed spring. The 1.5 kg cart moves off with a speed of 0.27 m/s. What is the velocity of the 4.5 kg cart after the spring is sprung?

2. A 1.0 kg ball traveling at 6.0 m/s collides head-on with a 2.0 kg ball moving in the opposite direction at a speed of 12 m/s. The 1.0 kg ball rebounds at a speed of 14 m/s after the collision. Find the velocity of the second ball.

4. A 0.105 kg hockey puck moving at 48 m/s is caught by a 75 kg goalie at rest. With what speed does the goalie slide on the ice?

Elastic and Inelastic Collisions

Inelastic collision:

Elastic collision:

Where does some of the mechanical energy go in an inelastic collision?

2. Is this collision elastic or inelastic? Justify your answer.

1. Find the final velocity of the two train cars after they latch together. Car 1 has a mass of 65,000 kg and moves at a velocity of 0.80 m/s. Car 2, with a mass of 92,000 kg, has a velocity of 1.3 m/s.

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