Laws of motion
Isaac Newton (1642-1727) is considered to be one of the greatest
thinkers of the last millennium:
Here are his four laws of motion:
1. A body will continue in its state of rest or uniform velocity unless acted on by an unbalanced force.
2. The rate of change of momentum of a body varies directly to the force causing the change and takes place in the same direction as the force
3. If a body, A exerts a force F on a body B then B exerts a force F on A - action and reaction are equal and opposite
4. If no external force acts on a system in a particular direction then the total momentum of the system in that direction remains unchanged.