Newton's Laws
A reference to this cornerstone of classical physics.
Newton's Three Laws of Motion (Mr. Wright's formulation)
  1. An object at rest remains at rest, and an object in motion remains in motion at a constant speed in a straight line, unless acted on by an unbalanced force.
  2. The unbalanced force on an object equals the object's mass multiplied by its acceleration.
  3. When an object puts a force on a second object, the second object puts an equal but opposite force on the first object.
It should be noted that there is no standard way to state in words Newton's laws of motion. As is often the case in physics, the actual definitions are strictly mathematical. Further, there are two mathematically equivalent frameworks in which to understand Newton's laws of motion:
  • One based on force and acceleration (the way students are usually first taught the laws), and
  • Another based on impulse and momentum (closer to the way Newton originally expressed the laws).