rigid bar pivoting on a fulcrum, producing mechanical advantage
one of six simple machines, alongside wheel, wedge, screw, pulley, inclined plane
three classes defined by relative positions of effort, load, and fulcrum
class 1: fulcrum between effort and load (seesaw, crowbar)
class 2: load between fulcrum and effort (wheelbarrow, nutcracker)
class 3: effort between fulcrum and load (tweezers, human forearm)
Archimedes: "give me a place to stand and I will move the Earth"
principle extends to hydraulic systems, pump mechanisms, and digital logic gates
energy input equals energy output minus friction losses