Question

When a body moves in a circular path, no work is done by the force since :

• A. force and displacement are perpendicular to each other.
• B. the force is always away from the centre.
• C. there is no displacement.
• D. there is no net force.

Answer 1

Answer: (A)

force and displacement are perpendicular to each other.

The work done by a force in moving a body is $W=\overrightarrow{F}.\overrightarrow{s}$

where $\overrightarrow{s}$ is the displacement vector.

In a circular path, the force is centripetal, thus always acting towards the center along the radial direction.

However the displacement is always along tangent to the circle at the instantaneous position of object.

Thus $W=\overrightarrow{F}.\overrightarrow{s}=0$