Question

A body is under the action of two equal and oppositely directed forces and the body is rotating with constant non-zero angular acceleration. Which of the following cannot be the separation between the lines of action of the forces?

• A. $1m$
• B. $0.4m$
• C. $0.25m$
• D. zero

Answer 1

The correct option is D zero

A pair of equal and opposite forces acting on a body is called a couple.

It only gives a rotating effect to the body and the torque due to a couple is

given by $\tau =Fd$

where $F$ is equal to the magnitude of one of the forces and

$d$ is the distance between their points of application.

To produce a non-zero angular acceleration , the torque on the body must be non zero.

Hence , the couple can give a non-zero angular acceleration to the body

only when the distance between the points of applications of the forces is non-zero.