# Work, Energy and Momentum

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• Created by: Sam Evans
• Created on: 17-02-15 21:40
When is work done by a force?
When a force moves through a distance
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What is the relationship between work and energy?
Work done = energy transferred
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What is the unit of power?
Watts, W
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What is the decrease in gravitational potential energy when an object of mass 6 kg is lowered through a distance of 9 m?
54 J
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What is elastic potential energy?
The energy stored in an elastic object when it is stretched or squashed
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What is the kinetic energy of a car of mass 1200 kg travelling at 30 m/s?
540 000 J
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What is the unit of momentum?
kg m/s or Ns
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What is the momentum of a 2500 kg truck travelling at 20 m/s?
50000 kg m/s
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Why is a gymnast less likely to injure herself is she lands on a thick foam mat gains 2 J of gravitational potential energy, calculate the height it is raised through.
The thick foam mat increases the impact time compared with the hard floor, reducing the force on the gymnast.
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The electronic motor in the question above has a power of 1.5 W. Calculate the time taken to raise the load.
2.0 m
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A trolley of mass 0.2 kg travelling at 1.5 m/s to the right collides with a stationary trolley of mass 0.3 kg. After the collision they move off together. Calculate the velocity of the trolleys after the collision.
1.3 s
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A trolley of mass 0.2 kg travelling at 1.5 m/s to the right collides with a stationary trolley of mass 0.3 kg. After the collision they move off together. Calculate the velocity of the trolleys after the collision.
0.6 m.s to the right
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## Other cards in this set

### Card 2

#### Front

What is the relationship between work and energy?

#### Back

Work done = energy transferred

### Card 3

#### Front

What is the unit of power?

### Card 4

#### Front

What is the decrease in gravitational potential energy when an object of mass 6 kg is lowered through a distance of 9 m?

### Card 5

#### Front

What is elastic potential energy?