Key Terms

complex machine
a machine that combines two or more simple machines
efficiency
output work divided by input work
energy
the ability to do work
gravitational potential energy
energy acquired by doing work against gravity
ideal mechanical advantage
the mechanical advantage of an idealized machine that loses no energy to friction
inclined plane
a simple machine consisting of a slope
input work
effort force multiplied by the distance over which it is applied
joule
the metric unit for work and energy; equal to 1 newton meter (N∙m)
kinetic energy
energy of motion
law of conservation of energy
states that energy is neither created nor destroyed
lever
a simple machine consisting of a rigid arm that pivots on a fulcrum
mechanical advantage
the number of times the input force is multiplied
mechanical energy
kinetic or potential energy
output work
output force multiplied by the distance over which it acts
potential energy
stored energy
power
the rate at which work is done
pulley
a simple machine consisting of a rope that passes over one or more grooved wheels
screw
a simple machine consisting of a spiral inclined plane
simple machine
a machine that makes work easier by changing the amount or direction of force required to move an object
watt
the metric unit of power; equivalent to joules per second
wedge
a simple machine consisting of two back-to-back inclined planes
wheel and axle
a simple machine consisting of a rod fixed to the center of a wheel
work
force multiplied by distance
work–energy theorem
states that the net work done on a system equals the change in kinetic energy