A body in motion tends to remain in motion; a body in rest tends to remain at rest. 2 parts: how fast you are going (speed, which way you are going (direction) Acceleration: how fast your velocity is changing speeding up slowing down changing direction. First law: an object that is not subject to any outside forces moves at constant velocity, covering equal distances in equal times along a straightline path. Second law: the force exerted on an object is equal to the product of the object s mass times its acceleration. The acceleration is in the same direction of the force. Easier to move a light object than a heavy one. Third law: for every force that one object exerts on a second object, there is an equal but oppositely directed force that the second object exerts on the first object. Need to consider all the forces acting on the body.