Question

A non-zero force is acting on a body but work done is zero. Which of the following statements can justify the above situation?
1. Displacement is zero.
2. Force is perpendicular to the direction of displacement.
3. Force is very high in magnitude.
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, $W=F\times d\times cos\theta$, where, d is displacement, F is the magnitude of the force and $\theta$ 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 $cos\theta$.
The value of $cos\theta$ is zero when $\theta$ is 90° i.e., force is perpendicular to the displacement.