Law of Inertia

An object at rest will remain at rest unless acted on by an unbalanced force. An object in motion continues in motion with the same speed and in the same direction unless acted upon by an unbalanced force

In bowling, the pins are at rest. They will remain that way until an external force (a 15 pound ball hurling down a lane) causes them to move

Force= Mass x Acceleration

Acceleration is produced when a force 
acts on a mass. The greater the mass
(of the object being accelerated) the
greater the amount of force needed 
(to accelerate the object).

Your friend is on a skateboard. You push him forward, and he moves. A little push, and he begins to move slowly. A big push, and he moves faster, and gains speed more quickly.

Action + Reaction

For every action there is an 
equal and opposite reaction

When you do a cannon ball into a pool,
you strike the water with some force and
 the water exerts an equal and opposite 
force on you