A body is moving along a circular path such that its speed always remains constant. Should there be a force acting on the body? A constant force acting on a body of mass 3.0 kg changes its speed from `2.0 ms^(-1)` to `3.5 m s^(-1)` in 25 s. The direction of motion of the body remains unchanged. What is the magnitude and direction of the force ?

Explanation

Force on a body moving in a circular path : Let a body of mass .m. is moving in a circular path of radius .r. with constant speed. The velocity of the body is given by the tangent drawn at that point. Since velocity is changing continuously the body will have acceleration.
So the body will experience some acceleration. This is called normal acceleration or centripetal acceleration.
Problem :: Mass of the body, m = 3.0 kg
Initial velocity of the body, `u = 2.0 ms^(-1)`
Final velocity of the body, `v = 3.5 ms^(-1)`
Time, `t = 25 s`
From Newton.s second law of motion,
`F = ma = (m(v - u))/(t) = (3.0 (3.5 - 2.0))/(25) = 0.18 N`
`therefore ` Magnitude of force acting on the body, F = 0.18 N. The direction of force acting on the body is along the direction of motion of the body because force is positive.