### First Law

An object will remain at rest or in uniform motion in a straight line unless acted upon by an external force.

e.g. if a car is at rest, then it will remain at rest until a force is exerted on it by either the engine or a person trying to push it.
If a car is moving at a constant velocity, then it will continue to do so until the engine applies more or less force on it, causing it to either accelerate or decelerate.

### Second Law

The rate of change of momentum is directly proportional to the force applied, and this change in momentum takes place in the direction of the applied force.

▵p ∝ F

e.g. If you use the same amount of force to move a bicycle and a car, the bicycle would have more acceleration because it has a smaller mass compared to a car.

### Third Law

If a body A exerts a force on body on body B, then body B will exert an equal and opposite force on body A.

e.g. A standing person of mass 70 kg exerts a force of 700 N on the ground (their weight). The ground will then exert an equal and opposite force on the person (-700 N).