CoachA simple machine is a device without a motor that changes a force to suit us: making it stronger, or changing its direction, or both. The classics: the lever you know from the seesaw and crowbar, the pulley, and the inclined plane — the humble ramp.
Examples
Example 31.2 (The lever, revisited)
The lever’s rule you already own: coins times marks — your small force far from the pivot beats a big load close to it. Notice something else now: your end of the crowbar sweeps a long way down while the boulder rises only a little. Keep that observation in your pocket; it is about to become a law.