A horizontal force, just sufficient to move a body of mass 4 kg lying on a rough horizontal surface, is applie on it. The coefficients of static and kinetic friction between the body and the surface are 0.8 and 0.6 respectivel If the force continues to act even after the body has started moving, the acceleration of the body (in `ms^-2` ) (take `g = 10 ms^-2`)

Options

A. 2
B. 4
C. 6
D. 8

Answer

A

Explanation

The acceleration of the body down the plane is `g sin theta-g(sin theta)=g(sin theta-0.5 xx cos theta)`. Thesefore, The body will first accelerate upto `x < 2 tan theta`. The velocity will be maximum at `x=2 tan theta,` because for `x > 2 tan theta`, the body starts decelareting.