Question

A pendulum is pulled back from its equilibrium (center) position and released.

(a) What form of energy is added to the system prior to its release? Explain.
a. The work in raising the pendulum bob has gone into gravitational potential energy.
b. The work in raising the pendulum bob has gone into kinetic energy.
c. No energy is added to the system prior to its release.

Answer 1

The energy added to a pendulum when it is pulled back is gravitational potential energy, which converts to kinetic energy as it swings.

Step-by-step explanation:

When a pendulum is pulled back from its equilibrium, the form of energy added to the system prior to its release is gravitational potential energy. As the pendulum bob is raised, work done against gravity is stored as potential energy. Upon release, this energy is converted into kinetic energy as the bob swings down. At the highest points in the swing, the pendulum has maximum potential energy and minimal kinetic energy. At the lowest point, all of the gravitational potential energy is converted into rotational kinetic energy, and the kinetic energy is maximal.

Evidence of this energy transformation is seen in the fact that the initial energy stored in the system is completely potential, and as the pendulum begins to move, the potential energy is converted into kinetic energy, peaking at the equilibrium position. The energy continues to oscillate between kinetic and potential as the pendulum swings.