# M1 OCR: some terms

the definitions for some words that typically come up on the exam paper

• Created by: Ayesha
• Created on: 28-05-12 10:30

## Tensions / thrust

A force acting along a string, spring, or rod

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## Normal Reactions

Equal and opposite forces between 2 bodies in contact

These act perpendicular to the common tangent between the bodies (along the common normal)

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## Friction

The force acting along the common tangent between the 2 surfaces

Opposes motion between the bodies

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## A Light String

We assume a light string has no weight

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## String over a smooth pulley

It has no friction

Equal tensions on each side

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## A string over a rough pulley

Rough = friction is acting on it

There are different tensions on either side

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## Equilibrium

When 2 or more forces act on it and motion doesnt take place

The sum of the components of the forces in any direction is zero

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## Particle

A particle is a body whose dimensions can be ignored

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