Newton’s First Law – Law of Inertia
Sir Issac Newton’s laws are basis for understanding human locomotion pathology of the lower limb is the result of the body attempting to violate the laws.
Law of inertia:
Every body continues in its state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by the forces acting on it. A body at rest will stay at rest unless a force acts on it.
A body in motion has momentum – the momentum will stay constant unless a force acts upon that body.
Momentum = mass x velocity