Work done by a force is zero when the angle between the force and the displacement is
Correct answer: C. 90 degrees
- A. 0 degrees
- B. 45 degrees
- C. 90 degrees
- D. 180 degrees
Explanation
Work is the scalar product Fd cos theta, and cos 90 degrees is zero, so a force perpendicular to the displacement does no work. This is why the centripetal force in uniform circular motion does no work and the speed stays constant. At 180 degrees the work is negative rather than zero, as with friction.
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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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