Question

In a system where a pendulum oscillates, at which specific point in its trajectory is the net work done on the bob by the tension force equal to zero, and why?

Accepted Answer

The net work done by the tension force on a pendulum bob is zero at every point along its entire trajectory. Work is defined in physics as the product of force, the distance moved in the direction of that force, and the cosine of the angle between them. For a pendulum, the tension force acts along the string, pulling directly toward the pivot point, while the bob&#x27;s instantaneous velocity is always directed tangent to its circular path. Because the string is perpendicular to the bob&#x27;s path of motion at every moment, the angle between the tension force and the direction of movement is always 90 degrees. Since the cosine of 90 degrees is zero, the tension force never contributes to the work done on the bob, regardless of its position. Think of this like a person walking in a perfect circle while holding a weight at the end of a rope; because they pull inward toward the center and never in the direction of the walking, they do no work on the weight even as it moves.

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In a system where a pendulum oscillates, at which specific point in its trajectory is the net work done on the bob by the tension force equal to zero, and why?

The net work done by the tension force on a pendulum bob is zero at every point along its entire trajectory. Work is defined in physics as the product of force, the distance moved in the direction of that force, and the cosine of the angle between them. For a pendulum, the tension force acts....