# Forces, Friction and Motion

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• Created by: kira
• Created on: 31-05-11 18:02

Forces and Friction

• When an object exerts a force on another object, it always experiences a force in return. These two forced can be called an 'interacton pair'.
• That means if you push against a wall, the wall will push back just as hard. As soon as you stop pushing, the wall stops pushing.
• An object resting on a surface experiences a reaction force.
• If a book is on a table , the weight of the book acts downwards, and the table exerts an equal and opposite force upwards on the book.
• The upward force is called a reaction force.
• When an object is moving relatively to another object, both objects experience a force in the direction that opposes the movement-this is friction.

a) Friction between solid surfaces which are gripping.

-This is a kinf of friction that can be found in the Earth's crust-big sections of rock sliding together but friction is forcing them to stay put.

b)Friction between solid surfaces which are sliding past each other.

-You can reduce sliding friction and gripping friction by putting something like oil or grease between the surfaces.

c) Resistance from fluids.

-This is an object moving through a fluid which has to…