Within the four-bar linkage family, there are more than a dozen well-known variations. The linkage that drives windshield wipers is probably the most popular example. A close second is the four-bar linkage that opens up inside your umbrella
Linkages seem like versatile tools just between these two examples.
You pull at the far end of the hammer handle with a light force, so a big force pulls the nail out with the hammer claw that is just a short distance from the hammer head. The hammer head creates a pivot point that acts as the fulcrum
I never thought about how a hammer has a shorter head than the length of the handle which creates the mechanical advantage.
a lever a single-mechanism machine
This definition makes sense after these terms are defined. Since it is a single moving piece that helps do work, it would be a single-mechanism machine.