Question

A person applies constant force $\overrightarrow{F}$ on a particle of mass m and finds that the particle moves in a circle of radius r with a uniform speed v as seen from an inertial frame of reference.

(a) This is not possible.
(b) There are other forces on the particle.
(c) The resultant of the other forces is $\frac{m{v}^2}{r}$ towards the centre.
(d) The resultant of the other forces varies in magnitude as well as in direction

Answer 1

(b) There are other forces on the particle.
(d) The resultant of the other forces varies in magnitude as well as in direction.

We cannot move a particle in a circle by just applying a constant force. So, there are other forces on the particle.
As a constant force cannot move a particle in a circle, the resultant of other forces varies in magnitude as well as in direction (because $\overrightarrow{F}$ is constant).