Work and Simple Machines

Humans use many different types of machines to apply force and perform work. It is critical that efficiency is optimized to conserve energy. But what exactly do all of these terms - force, work, energy, efficiency - mean and how are they related?
This course defines and explains the relationships between force, work, power, energy, and efficiency. It also describes how several simple machines - inclined planes, levers, gears, wheels, pulleys, and hydraulics - can be used to transmit forces and sometimes amplify them or change their direction. The mechanical advantage provided by machines is improved by minimizing friction, which always opposes motion.