# Mechanics in Unit 2 physics

A summarisation of the mechanics in unit 2 physics

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• Created by: Rachel
• Created on: 10-01-13 15:51

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Newton's laws of motion
1st law
"The velocity of a body remains constant unless acted upon by an external force"
An object will remain still or move in a straight line at constant speed unless there is additional force
acting upon it.
If forces are not balanced, the resultant force makes the body accelerate-change in direction and/or
speed
2nd law
Resultant force (N) = Mass (kg) x Acceleration (ms¯²)
OR
F=ma
The more force acting on a mass, the more acceleration you get (directly proportional)
For a given force the greater the mass the less the acceleration (inversely proportional)
All objects fall at the same rate as acceleration is independent of mass
3rd law
If object A exerts a force on object B, then object B exerts an equal but opposite force on object A
Every action has an opposite and equal reaction
The pair of forces must be the same type
Work and power
Work is done when energy is transferred from one form to another
Work done (J) =force causing motion (N) x distance moved (m)
W=Fs
Power= Work done per second = the rate of doing work= amount of energy transformed per
second
Power (Watts) = work done (J)/ time (t)
P=W/t= Fs/t =Fv

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