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Momentum and collisions

Momentum and collisions

1.[2p]

A 0.20 kg ball arrives at 25 m s⁻¹ and leaves at 20 m s⁻¹ in the opposite direction. What is the magnitude of the impulse, in newton seconds?

CorrectNot quite: 9.0

2.[2p]

Why does an airbag reduce the force on a driver?

Correct
The answer is: It lengthens the time over which the same momentum change happens
The answer is: It lengthens the time over which the same momentum change happens
The answer is: It lengthens the time over which the same momentum change happens

3.[2p]

A 1500 kg car at 18 m s⁻¹ hits a stationary 1000 kg car and they lock together. What is their common speed, in metres per second?

CorrectNot quite: 10.8

4.[1p]

Momentum is conserved in a perfectly inelastic collision.

Correct
The answer is: True

5.[2p]

Which law is momentum conservation a direct consequence of?

Correct
The answer is: Newton's third law, which makes the internal forces of a system cancel in pairs
The answer is: Newton's third law, which makes the internal forces of a system cancel in pairs
The answer is: Newton's third law, which makes the internal forces of a system cancel in pairs

6.[3p]

A 3.0 kg body moving at 5.0 m s⁻¹ collides elastically with a stationary 1.0 kg body. What is the final speed of the 1.0 kg body, in metres per second?

CorrectNot quite: 7.5

7.[3p]

Which of these are true of an elastic collision in one dimension?

Select all that apply

Correct
Correct
Correct
The answer is: The relative speed of separation equals the relative speed of approach, Equal masses exchange velocities when one is initially at rest, A very light body striking a very heavy stationary one rebounds at almost its original speed

8.[3p]

A 12 g bullet embeds in a 3.00 kg ballistic pendulum block, which then rises 0.125 m. What was the bullet's speed, in metres per second?

CorrectNot quite: 393

9.[3p]

Match each stage of the ballistic pendulum to the law that applies to it.

  • The bullet embedding in the block

  • The block swinging upward

  • The whole experiment

  • Using energy conservation across the impact

  • momentum first, then energy

  • momentum conservation, with most kinetic energy lost

  • gives an answer far too small

  • mechanical energy conservation

Show the answer

The bullet embedding in the block: momentum conservation, with most kinetic energy lost The block swinging upward: mechanical energy conservation The whole experiment: momentum first, then energy Using energy conservation across the impact: gives an answer far too small