If object X applies a force onto object Y, then object Y simultaneously applies the same size force back onto object X.
OR
For every force or action , there is an equal but opposite force or reaction.
N(III) is applicable in all situations, whether an object is:
- at rest (NI),
- or whether it is moving at constant velocity (NII)
- or if accelerating (NIII).
Important Points
- N(III) is a lot about TWO OBJECTS
- and the interacting forces that "connect" them.
- Each of the two equal sized forces, act on one object only.
- So these pair of forces CANNOT CANCEL each other since they are acting on DIFFERENT objects.
Some Examples
If You Slap Yourself
Two Trolleys Moving Apart
Two trollets are held as shown, with a compressed spring in an isolated system.
The trolleys are simultaneously released.
