• Revision:Newtons laws of motion

TSR Wiki > Study Help > Subjects and Revision > Revision Notes > Mathematics > Newton's Laws of Motion


1st Law

  • An object will remain in a state of rest or in uniform motion in a straight line unless acted on by an external net force.

2nd Law

  • The acceleration of a body, acted upon by an external net force, is directly proportional to the force being applied and inversely proportional to the body's mass.
  • Force = Mass x Acceleration

This can be mathematically notated as: F = ma

If the mass is assumed to be constant, and either the acceleration is an average, or is also constant: F = \frac{m(v-u)}{t}\quad \because\quad a = \frac{v-u}{t}.

For A Level maths and physics the following may also be useful:

The rate of change of momentum of a body is equal to the external net force being acted upon it, acting in the direction of the applied force"

3rd Law

  • If body A exerts a force on body B, body B will simultaneously exert a force of equal magnitude, but opposite direction, on body A


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