Input Force

Real World Example

Imagine you're trying to open a stubborn jar of pickles. Just like the effort you exert with your hand to twist the lid, the input force is the effort applied to a machine to make it work. The twisting motion of your hand represents the input force, and the jar lid is the machine you're attempting to operate; without that initial twist, the jar won't open, just as a machine won't function without an input force.