5.1a The motion of an object is always judged with respect to some other object or

point. The idea of absolute motion or rest is misleading.

5.1b The motion of an object can be described by its position, direction of motion, and speed.

5.1c An object’s motion is the result of the combined effect of all forces acting on the

object. A moving object that is not subjected to a force will continue to move at a constant speed in a straight line. An object at rest will remain at rest.

5.1d Force is directly related to an object’s mass and acceleration. The greater the force,

the greater the change in motion.

5.1e For every action there is an equal and opposite reaction.