Work is done on a body only when
Correct answer: B. a force acts and the body moves with a component of displacement along the force
- A. a force acts on it
- B. a force acts and the body moves with a component of displacement along the force
- C. the body is at rest
- D. the body has energy
Explanation
Work is the dot product of force and displacement, so a porter standing still holding a heavy suitcase does no work on it however tiring it feels. Carrying it horizontally also does no work against gravity, since the weight is vertical and the displacement horizontal. The joule is the work done when a force of one newton moves its point of application one metre.
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About Work
Work is done when a force produces displacement, with its value determined by the component of force along the displacement. The topic covers positive, negative and zero work, work by variable forces from force-displacement graphs, and the connection between net work and change in kinetic energy.
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