Question

(i) What happens to the work done when the displacement of a body is at right angle to the direction of force acting on it? Explain your answer.
​(ii) A force of 50 N acts on a body and moves it a distance of 4 m on a horizontal surface. Calculate the work done if the direction of force is at an angle of 60° to the horizontal surface.

Answer 1

(a) Work is done when a body is displaced in the direction of the force. If force is perpendicular to the direction of displacement, then it simply means that no component of force is taking part in moving the body in the direction of given displacement.

Hence, the work done by a force is zero, when it is at the right angle to the direction of displacement of the body.

(b)


Here, F = 50 N, Displacement, d = 4 m

The angle between the force and the displacement = $60°$

Work is done when the body is displaced in the direction of the force.

So, the component of force in the direction of displacement = $F\cos 60°$ = $\frac{F}{2}$

Work done, $W=\frac{F}{2}\times d=\frac{50\mathrm{N}}{2}\times 4\mathrm{m}=100\mathrm{J}$

Hence, the work done by the given force is 100 J.