Question

Five forces are separately applied to the flat object lying on a horizontal table of negligible friction as shown in the figure above. The line of action of each force is shown by a dashed line. Identify which of the five forces will cause the object to rotate about point $O$?

• A. A
• B. B
• C. C
• D. D
• E. E

Answer 1

The correct option is C C

In order for a force to cause rotation about a point, the torque due the force about that point should be finite.

Torque of a force about a point with minimum distance from the line of force $r_L=F.r_L$

For all forces except C, the value of $r_L$ is zero since the line of force passes through the point O itself.

Hence correct answer is option C.