Question

A person applies a constant force 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 mv²/r towards the center.
(d) the resultant of the other forces varies in magnitude as well as direction.

Answer 1

Answer ⇒ Option (b). and Option (d).

Explanation/Reason ⇒  When the constant force is applied to a particles then it will move in circular path. At its initial position, the Forces will be different but as it starts moving then there will be some other forces to balance it because F is constant.

Hence, Option (b). is correct.

Now, At every positions the Value of the Forces on the object will vary because they can only balance the body when they will change in magnitude as well as direction. Thus, there Resultants also changes.  

Therefore, Option (d). is also correct.

Hope it helps .