Physics (P2) - Work, Energy and Momentum

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• Created by: Roma
• Created on: 14-12-13 08:50
What is needed for object to move?
A force must be applied to it.
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What happens when a force moves an object?
Energy is transferred and work is done.
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What happens when work is done?
The supplied energy is transferred to the object as the work done is equal to the energy transferred.
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What is gravitation potential energy?
Where energy is stored in an object because of its position in the Earth's gravitational field.
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What happens when an object is moved vertically upwards?
It gains gravitational potential energy equal to the work done on it by the lifting force.
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What is power?
The rate of transfer of energy.
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What is kinetic energy?
Energy which all moving objects have. The greater the mass of an object and the greater the speed, the more kinetic energy it has.
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What is momentum?
Energy which all moving objects have. The greater the mass of an object and the greater the velocity, the greater the momentum.
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What is the law of conservation of momentum?
Whenever objects interact, the total momentum before the interaction is equal to the total momentum afterwards - provided no external forces act on them. This means the total change in momentum is zero.
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What could the two interactions between the objects be?
A collision or an explosion. After a collision the objects may move together, or move apart.
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What does momentum have?
Size and direction. In calculations, one direction is positive, so the momentum in the other direction must be negative.
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What happens when two objects push each other apart (explode)?
They move apart at different speeds if the they have unequal masses. They move apart with equal and opposite momentum so their total momentum is zero.
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What happens when a force acts on an object that is able to move?
Its momentum changes. For a particular change in momentum, the longer the time taken for the change, the smaller the force that acts.
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What happens to momentum in a collision?
The momentum of the objects often becomes zero during the impact because it stops moving.
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What effect does impact time have?
If impact time is short, the forces on the object are large. As the impact time increases, the forces become less.
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What is a crumple zone in a car and how does it work?
An area of a car which is designed to fold in a collision This increases the impact time and so reduces the force on the car the people in it.
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What do air bags do?
Spread the force on the body across a larger area. If you hit the air bag it changes momentum slowly , so the force is less than if it changed momentum quickly by hitting the steering wheel.
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What do seat belts do?
Spread the force on the body across a larger area. They stop the wearer being flung forward if the vehicle suddenly stops. The seatbelt stretched slightly, increasing the impact time and reducing the force.
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How can you calculate the speed of a vehicle before it has crashed?
Use measurements from the scene and conservation of momentum.
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Other cards in this set

Card 2

Front

What happens when a force moves an object?

Back

Energy is transferred and work is done.

Card 3

Front

What happens when work is done?

Card 4

Front

What is gravitation potential energy?

Card 5

Front

What happens when an object is moved vertically upwards?