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Question
A person applies constant force \[\overrightarrow{\text{F}}\]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 \[\frac{\text{mv}^2}{\text{r}}\] towards the centre.
d) The resultant of the other forces varies in magnitude as well as in direction
Solution
(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\[\overrightarrow{\text{F}}\] is constant).
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