Key Idea: A moving object will maintain the same speed and direction of motion unless a force acts on it.

Students are expected to know that:

  1. If no forces (or forces that add to zero) act on a moving object, then the object will maintain a constant speed.
  2. If an object is maintaining a constant speed (or is at rest), then no forces (or forces that add to zero) are acting on it.


  1. Students are expected to analyze situations involving no more than two forces acting on an object at the same time, and each force must act along the object’s line of motion.
  2. Items will not include situations in which objects are at rest.