• Created by: MahiraU
  • Created on: 10-05-21 16:57


A force can be a push or a pull. These are called applied forces. When a force is exerted on an object, it can change the object's: speed, direction and shape. Forces are measured in Newtons. A force meter/newton meter is used to measure forces. The results are in newtons. 

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Hooke's Law

Hooke's Law - a law stating that the strain in a solid is proportional to the applied stress within the elastic limit of that solid.

Units: N/m, N/cmor Pascal (Pa)

For example, when applying stress to a spring and it exceeds its elastic limit, it can no longer go back to the way it was.

There are elastic objects and plastic objects.

Elastic - when an object can return to the shape it was.

Plastic - when an object can't return to the shape it was.

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Friction is a force between two surfaces that are sliding, or trying to slide, across each other. For example, when you try to push a book along the floor, friction makes this difficult. It always works in the direction opposite to the direction in which the object is moving, or trying to move. It always slows a moving object down.

Friction also produces heat. For example, if you rub your hands together quickly, you will feel them get warmer.

Another example, is when you are driving your tyres and the road are being applied with friction, enabling the car to driving without the car slipping and sliding across the road. 

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Pressure = force per unit area.

The pressure a solid object exerts onto another solid surface is its weight in newtons divided by its area in square metres. To work out pressure, you use the following equation:

pressure = force/area

p = f/a

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Unbalanced Forces

Unbalanced forces - when two forces acting on an object are not equal in size.

The overall force acting on the object is called the resultant force. If the forces are balanced, the resultant force is zero. If the forces on an object are unbalanced, this is what happens: 

A stationary object starts to move in the direction of the resultant force.

A moving object changes speed and/or direction in the direction of the resultant force.

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