A child is revolving a tiny 10g stone, tied at one end of a string, in a vertical loop of 2m diameter. If the stone completes 100 revolutions in 1 second, the work done on it will be:
Correct answer: A. Zero
- A. Zero
- B. 19.8 J
- C. 4.9 J
- D. 9.8 J
Explanation
W = F.dW = Fd cosθ = Fd cos90° = Fd (0) = 0Due to centripetal force the stone will move in a circular path. In the circular path, the centripetal force 'Fc" is perpendicular to velocity "v".As the displacement "d" is parallel to the velocity "v". So the angle between the displacement "d" and the centripetal force "Fc" is 90°.
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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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