Summary
Work done by a constant force is the product of force and distance and the
resulting change of energy W = Fd cos θ.
Forward forces do positive work, backward forces do negative work,
perpendicular forces do no work.
Work done by a variable force is measured by graphing F versus the
horizontal, and then finding the area bounded by the graph of F, the x-axis, and
vertical lines indicating the beginning and end of the period of force.
Kinetic energy refers to the energy an object possesses by virtue of its motion
and equals mv^2.
The work–energy theorem states that the total work done on an object is equal
to the object’s change in kinetic energy.
Potential energy is the energy an object has by virtue of its position. Work
done on an object to put it in a given position is stored in the object that can be
retrieved.
Conservation of mechanical energy is the sum of an object’s kinetic and
potential energies. Nonconservative forces, such as friction, are disregarded,
so the initial mechanical energy is equal to the final mechanical energy.
Power is the measure of work over time. It is the rate at which work is
done.
Gravitational potential energy comes into play when the height is large
compared with the earth’s radius. In this case, gravitation is a variable force.
