A horizontal force just sufficient to move a body of mass `4 kg ` lying on a rought horizontal surface is applied on it .The coefficient of static and kinetic friction the body and the surface are `0.8 and 0.6` respectively If the force contines to act even after the block has started moving the acceleration of the block in `ms^(-2)` is `(g = 10 ms^(-2))`

Options

A. `1//4`
B. `1//2`
C. 2
D. 4

Answer

C

Explanation

The minimum force required to just move a body will be `f_(1)=mu_(s)mg` . After the motion is started, the friction will become kinetic. So the foprce which is responsible for the increase in velocity of the block
`F=(mu_(s)-mu_(k))mg=(0.8-0.6)xx4xx10=8N`
So `a=(F)/(m)=(8)/(4)=2m//sec^(2)` .