What should be the angle between the force and displacement so that the work done is
(i) zero (ii) maximum?
Answers
Answer:
maximum is a right answer
Answer:
(i) zero: cos 90° = 0, Ф = 90°
(ii) maximum: cos 0° = 1, Ф = 0°
Explanation:
(i) zero: When the displacement is normal to the direction of force, i.e., value of Ф = 90°, then cos 90° = 0. Hence, the work done is zero.
Example: While a collie walks on a horizontal ground while carrying a load on his head, no work is done against the force of gravity because the displacement of load is normal to the direction of force of gravity which is vertically downwards, so the work done is zero.
(ii) maximum: If the displacement is in the direction of force, i.e., Ф = 0°, then cos 0° = 1, Work done will be positive which is maximum.
Example: In free fall of a body of mass m under gravity through a height h from A to B (say) ,the force of gravity F = (mg) is in the direction of displacement s = (h) and the work done by the force of gravity is W = FS = mgh, so the work done will be the maximum.