A boy holds a 400 N weight at arm's length for 10s. His arm is 1.5m above the ground. The work done by the force of the boy on the weight while he is holding it is:
Correct answer: A. 0
- A. 0
- B. 900J
- C. 600J
- D. 400J
Explanation
Holding stationary means zero displacement of the weight in direction of the force, so the work done by the boy's force is zero despite the metabolic effort. Therefore option A iscorrect.
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About Work and Energy
Work transfers energy when a force causes displacement, while kinetic energy, gravitational potential energy and power describe motion, position and the rate of energy transfer. The work-energy theorem links net work with change in kinetic energy, and efficiency accounts for energy losses rather than treating them as energy destruction.
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