# As fast as you can!

Physics

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• Created by: charlotte
• Created on: 05-06-11 09:58

## Speed...

....describes the movement of the object.

Velocity-is an objects speed in a stated direction. This is called the vector quantity. The direction of velocity is indicated by a - or + sign. If a car was travelling +40mph and another is travelling -40mph they are simply traveling in oppisite directions.

Displacement is used to describe the distance covered in a certain direction. It is another vector quanity.

The accelertaion of an object is the rate at which its velocit changes. It is a measure of how quickly an object is speeding up or how slowly an object is slowing down.It is measure in m/s(2)

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## Velocity-Time Graphs...

The slope of a velocity time graph represents the acceleration of an object- (the steeper the gradient the greater the acceleration). The area underneath the line represents the total distance travelled.

Forces- are pushes or pulls. eg friction, weight and air resistance. Forces may be different sizes and act in different directions. It is measured in NEWTONS (N)

Stationary objects- have equal forces acting upon them

Action force- When object A pushes of pulls object B

Reaction force-When object B pushes or pulls object A

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## How forces affect movement...

Resultant force- is the balance of forces acting upon something.

Accelerating- When the driving force is greater that the resistive force.

Braking-When the resistive force is greater than the driving force

Moving at a constant speed-When the driving an resitive force are equal

If an unbalanced force acts on an object then the acceleration of the object will depend on...

• the size of the unbalanced force-the bigger the force, the greater the acceleration
• the mass of the object-the bigger the mass, the smaller the acceleration.
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## Terminal Velocity

the constant velocity reached by a falling body (gravitational force is equal to the frictional forces acting upon it).

Falling objects experience two forces...

• the downward force of weight which always stays the same
• the upward force of resistance or drag

Stopping Distances-

depend on the thinking distance and the braking distance.

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## Stopping Distance cont...

Factors affecting stopping distances..

The speed of the vehicle

The mass of tehe vehicle

The conditions of the vehicle and road

The drivers reaction time

Momentum- is the measure of the state of movement of an object. It is dependant on two things;

The mass of the object

The Velocity of the object

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## Safety Technology

cars have a lot of safety features to try and minimise injury and reduce the number of deaths;

• crumple zones- absorb momentum
• power assisted steering and anti-lock brake systmes- help the driver control direction
• cushioing during impact
• seatbelts which lock when the car brakes

imposed risk - eg coal mining, operating machinery

voluntary- smoking, rock climbing

Displacement- a disnce covered in a certain direction

Magnitude- a measure of size

Vector- a quanity that has both size and direction

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