# P3 OCR

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- Created by: Nick
- Created on: 26-05-11 19:36

First 391 words of the document:

Physics Revision P3

P3a

Speed = rate of change of distance. Speed = Distance / Time

Distance = Speed * Time

Time = Distance / Speed

Distance Time graphs = Displays data on distance and time. To calculate each gradient use the

equation speed = distance / time.

Distance time graphs can give you an overview of a journey. Comparing gradients can tell you

about the speeds.

P3b

Acceleration = Rate of increase of velocity. Calculating acceleration depends on two things, how

much the speed of the object changes and how long the change in speed takes. Equation --

Acceleration = Change in speed / time. OR . Metres per second squared = Metres per second squared /

seconds.

Speed-time graphs can help us understand acceleration. Looking carefully at one you can work

out specific speeds, times and acceleration.

P3c

Stopping Distances = The distance a vehicle travels from the time the driver sees a hazard to

when the vehicle comes to a rest (thinking distance + braking distance)

When you need to stop, a small amount of time is spent deciding whether or not to put your

foot on the brakes. This is the thinking distance. Can be increased by use of alcohol, tiredness and use of

drugs.

After you put your foot on the brake the car slows down but it continues to travel until it stops.

This is the braking distance. Can be increased by wet roads, icy roads, brakes not working properly,

worn down tyres.

Force = mass * acceleration (Newtons = kg * metres per second squared)

P3d

The energy transferred when a force moves an object (work = force * distance)

Two things that will make someone use up energy quicker = Having to push with a greater force,

having to push for a greater distance.

Power = Measured in Watts. It is a measure of how quickly work is being done and energy is

being transferred. It is how much work is done in one second, OR, how much energy is transferred in one

second.

P3e

Transport all need a source of energy that is transferred into kinetic energy causing movement.

Fossil fuels = Petrol, Diesel and other non-renewable sources.

Kinetic Energy = 0.5 * mass * velocity (J = 0.5 * Kg * [m/s²])

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