Question

A force F acts on a body and displaces it by a distance S in a direction at an angle θ with the direction of force.
(a) Write the expression for the work done by the force.
(b) What should be the angle between force and displacement so that the work done is (i) zero, (ii) maximum?

April 8, 2024

Answer

(a) When force acts at an angle θ to the direction of displacement then work done is

W = F × S Cos θ

(b) (i) For work done to be zero the angle between force and displacement should be equal to 90° as cos 90° = 0

Therefore, the product will also be zero.

W = F × S Cos 90° = 0

(ii) For work done to be maximum the angle between force and displacement should be equal to 0° as cos 0° = 1

Therefore, the product will also be maximum.

W = F × S Cos 0° = F × S

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