Question

A non-zero force is acting on a body but work done is zero. Which of the following statements justify the above situation?

1.Displacement is zero.
2.Force is perpendicular to the direction of displacement.
3.Force is parallel to displacement.
4.Force is opposite to the direction of displacement.

• A. 1 and 3
• B. 1 and 2
• C. 1 and 4
• D. 1, 3 and 4

Answer 1

The correct option is B

1 and 2

The mathematical equation for work done is given as, W = F $\times$ d $\times$ cos (a), where, d is displacement, F is the magnitude of the force and a is the angle between force and direction of displacement. Now, since force is non-zero, there are only two variables in the equations that make the work done zero i.e., displacement and cos (a). The angle cos (a) is zero when 'a' is 90° i.e., force is perpendicular to the displacement.