Q:

# How does a pendulum work?

A:

Once a pendulum is moved, simple gravity is what keeps it swinging. Sometimes additional means are used such as weights, pulleys and springs.

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A grandfather clock is an iconic example of a machine that uses a pendulum. One back and forth movement of the pendulum is referred to as a period. If a pendulum's period is 4 minutes, that means it takes 2 minutes for it to swing one way and 2 minutes to swing another. As the pendulum swings, the minute hand marks off time on the clock face.

While some older clocks with pendulums work by a person manually starting the pendulum swinging, most have either weights or a spring. In a weighted pendulum clock, the weights hang from the main mechanism on chains. When the pendulum starts swinging, the weights are at the top. As the pendulum swings, the weights lower, which transfers their potential energy to the pendulum to keep it moving. Once the weights reach the bottom, the pendulum stops.

A clock with a spring mechanism works on the same principle. The coiled springs' potential energy powers the pendulum. Once the spring is uncoiled, the pendulum stops. Instead of weights being pulled to start the pendulum, a key is used to wind the clock, which coils the spring.

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## Related Questions

• A:

To build a ballistic pendulum, use a cardboard box, weights, four eye hooks, nylon string, a piece of plywood and a sheet of white paper. Mount the ballistic pendulum after it is constructed.

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• A:

The force of gravity is the only force that keeps a standard hanging pendulum in motion. It is both the force that increases the speed of the pendulum on its downswing and decreases its speed on its upswing. The force of friction from air is the major reason that the arc of the pendulum's swing diminishes over time.

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• A:

The physical parameters in a simple pendulum experiment are a small-diameter bob and a string that has negligible mass, according to OpenStax College. The string should not be elastic, however.