**Newton's Three Laws of Motion**

## Number One

An object in

Vice versa, a

**motion**will not**stop**unless an**external force**acts upon it. This is the**principle of momentum**Vice versa, a

**stationary**object will not**move**unless an**external force**acts upon it. This is the**principle of inertia**## Number Two

An

This is best described via the equation

The

**external force**applied to an object can change it's**direction or acceleration**This is best described via the equation

**F = ma**The

**rate of momentum**is proportional to the**net force**applied## Number Three

For every

For

This shows how

**action**there is an**equal**and**opposite reaction**For

**example**:**Take a Simple Punch**This shows how

**reaction forces**affect the**impact**but don't make the punch**obsolete**due to different**object masses**
Here the arm is being pushed forward with a force of 80NHowever there is an equal and opposite reaction pushing the body back with a force of 80NNow because the body has greater mass, it doesn't move back at the same rate as the arm due to Newton's second law. However, it does move backwards and this means that the punch has less impact on the object it is impacting. |

Here the same force is being punched with, with the same reaction force This time though the body has pushed back 60N giving a reaction force of 60NBecause the body has a larger mass this means the reaction force pushes the arm forwards at a faster rate using Newton's second lawThis means overall the forward punch has a greater force |

**Momentum and Inertia**

**Momentum**and

**Inertia**are effectively the

**same thing**

They are both the

**unwillingness**of an object to change what it is doing.

Momentum is applied to objects already moving

Inertia is applied to objects stationary

Momentum is given the symbol

**'**

**p'**

Momentum is

**defined by**

momentum (kg m/s) p = mv mass (kg) x velocity (m/s)

**Conservation of Momentum**

*The*

**momentum**of a**closed system**remains**constant**unless an**external force**is applied**Impulse**

*Impulse is the change in momentum of an object*

This can be worked out by using the equation

**Δ**p

**= m**Δv = mv - mu

To work out the rate of change you

Which also shows us the

**divide by time**Which also shows us the

**connection between Force**and**Momentum**

The**rate of change**in momentum**equals**the**force**of the object

__Δ__**Thus**

t

__p__= Rate of change in momentumt

**Δ**

__p__=**Which looks like**

__m(v-u)__

t t**Therefore**

t

__m(v - u)__= Ft

__Δ__

t

__p__= Ft