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Physics P4

A: Forces in all directions
Forces are needed to change the motion of an object, and are the pushes and pulls

experienced by an object when it interacts with another.

Forces can be represented by an arrow.

Forces arise from interactions between two objects.

Forces always come in…

Page 2

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When you walk, your feet exert a backward force on the surface to move you forward,

so it is more difficult to walk on icy surfaces.

Page 3

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C: Friction
Friction is the force exerted on an object due to the interaction between it and

another object that is sliding over it that is caused by the roughness of both surfaces.

Friction adjusts its size in response to the situation up to a limit.

The limit depends on…

Page 4

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E: Adding forces

If there is a force on an object, but the object is not moving, there must be another force

cancelling it out.

If forces balance each other, they are said to add to make zero.

Resultant force is the sum of all the forces acting on an…

Page 5

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Truvelo speed cameras use detector cables in the road at a particular distance apart,

which sense when a car is driving over them and uses computers to calculate the vehicles

speed.

Police radar guns bounce microwaves off the approaching cars, and use the change in

frequency between the reflected and…

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Tachographs are installed in lorries to monitor the drivers speed and time spent

driving before having a break.

Tachograph traces are speed-time graphs.

Velocity-time graphs are similar to speed-time graphs, but also show the

direction an object is travelling.

A negative velocity means the object is travelling in the opposite…

Page 7

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Crumple zones increase the time for which the force of the collision acts, reducing the

force exerted on the car.

Seat belts and air bags work similarly to crumple zones, increasing the time taken for the

change in momentum.

It is not possible to save yourself using your arms or…

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Gravitational potential energy is the energy an object depending on its

height above the ground, and is defined by the equation:

o GPE (J) = weight (N) x vertical height difference (m)

Kinetic energy is the amount of energy an object has due to its motion, and is

defined by…

Page 9

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Physics P5

A: Static electricity
Static electricity is an electric charge that has built up on an object.

Plastic can become charged by rubbing it against an object.

Two charges the same repel.

Two different forces attract.

Electric charge is the overall charge that occurs when electrons are added or…

Page 10

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Electric fields are regions around an electric charge where the effects of the

charge can be felt, causing a force.

Electric current is the flow of electric charges around a circuit.

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