# P2 Work, Energy and Momentum

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• Created by: KAustria
• Created on: 17-05-14 14:11
In terms of energy transfer, what happens when an object moves?
A force moves an object, energy is transferred and therefore work is done
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Work done is equal to what?
Energy transferred
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What are the two variables which determine how much work has been done?
The force in Newtons and the distance in which the object has moved.
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What is energy transferred into to overcome fiction?
Thermal energy
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Define Gravitational Potential energy
Ther energy stored in an object because of its position in the Earth's gravitational field.
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How does an object gain gravitational potential energy?
When it is moved vertically upwards it gains GPE which is equal to the work done it by the lifitn force.
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What are the 2 variables which determine an objects gravitational potential energy?
1. Mass in kgs 2. Height in m
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What is power?
The rate of transfer
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What is power measured in?
Watts
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How can a moving object gain more kinetic energy?
The greater its mass and the faster the speed of the object
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What is an elastic object?
An object that regains its shape after being stretched or squashed
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What is energy transferred to when an object is stretched or squashed?
Elastic potential energy
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When a spring is squashed and released it warms up. Why?
This is because the elastic potential energy stored due to it being squashed, has been released as it has gained its original shape.
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Why does an object have great momentum?
Because it has a large mass and great velocity
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What is the equation of momentum?
p = m x v (momentum = mass x velocity)
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What is the law of conservation of momentum?
The law that states that the total momentum before object interact is equal to the total momentum to the afterwards - provided no external forces act on them.
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When an object is at rest what is its momentum?
0
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IN an explosion two object moves apart, what are its momentum?
The two objects move apart with equal and opposite momentum: one being positive and the other negative. This means that the total momentum is 0
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What happens to an object moving and an external force acts on it?
Its momentum changes
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For a change in momentum, how do you increase impact time?
By decreasing the force
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If the impact time is short what are sizes of the forces acting on the object like?
Large
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What is impact time?
The time it takes for a collision to take place
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What feature of a car increases impact time?
Crumple zones increase impact time by folding in a collision. This reduces the force on the car and people in it.
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Name other car features which increase impact time
1. side impact bars 2. crumple zones 3.Seat belts 4. Air bags
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Explain how a seatbelt and air bags work together in increasing impact time?
They spread the forces on the body across a larger surface area. Air bags change momentum slowly so the forces on the head is less. Seat belts prevent the wearer from being flung forward.
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## Other cards in this set

### Card 2

#### Front

Work done is equal to what?

#### Back

Energy transferred

### Card 3

#### Front

What are the two variables which determine how much work has been done?

### Card 4

#### Front

What is energy transferred into to overcome fiction?

### Card 5

#### Front

Define Gravitational Potential energy