A body is moving down a long inclined plane of angle of inclination . The coefficient of friction between the body and the plane varies as = 0.5 x, where x is the distance moved down the plane. The body will have the maximum velocity when it has travelled a distance x given by
The acceleration of the body down the plane is .
Therefore, the body will first accelerate up to x < 2 tan .
The velocity will be maximum at x = 2 tan ,
because for x > 2 tan , the body starts decelerating. Hence, the correct choice is (a).