Flashcards in P2 3 Energy And Momentum Deck (19)

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## When is work done on an object?

### Work is done on an object when a force makes the object move.

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## What is the equation for work done?

### Work done (J) = force applied (N) x distance moved in the direction of the force (m).

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## What is work done to overcome friction transferred as?

### Work done to overcome friction is transferred as energy that heats the objects that rub together and the surroundings.

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## What is energy transferred the same as?

### Work done.

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## What does the gravitational potential energy of an object depend on?

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• The weight of the object

• How far the object moves vertically

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## When does the gravitational potential energy of an object increase?

### The gravitational potential energy of an object increases when the object goes up and it decreases when the object goes down.

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## What is the change of gravitational potential energy equation?

### The change of gravitational potential energy (J) = its weight (N) x its change of height (m).

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## What is gravitational potential energy?

### Gravitational potential energy is energy stored in an object because of its position in the earth's gravitational field.

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## What does the kinetic energy of an object depend on?

### The object's mass and the object's speed.

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## What is the kinetic energy equation?

### Kinetic energy (J) = 0.5 x mass (kg) x speed^2 (m/s^2).

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## What is KERS (kinetic energy recovery systems)?

### KERS store energy when a vehicle brakes and it uses the energy later. Kinetic energy can be transferred to a flywheel for use in braking or overtaking.

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## What is elastic potential energy?

### Elastic potential energy is the energy stored in an elastic object when work is done on it to change its shape.

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## What is momentum?

### Momentum (kg m/s) = mass (kg) x velocity (m/s).

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## What does the law of conservation of momentum state?

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The law of conservation of momentum states that in a closed system, the total momentum before an event is equal to the momentum after the event.

Momentum is conserved in any collision or explosion provided that no external forces act on the objects.

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## What happens to the movement of two objects when they push each-other apart?

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• They move apart with different speeds if they have unequal masses

• They move apart with equal and opposite momentum so their total momentum is zero

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## Conservation of momentum in recoil situations:

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(Mass of A x velocity of A) + (mass of B x velocity of B) = 0.

Momentum = 0 as both objects were at rest.

Rearrange the equation to give:

(Mass of A x velocity of A) = - (mass of B x velocity of B).

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## When vehicles collide, what does the force of the impact depend on?

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• The mass of the vehicles

• The change of velocity of the vehicles

• The duration of the impact

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##
Fill in the gap:

The longer the impact time is, the ... the impact force is reduced.

### More.

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