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 ti just move a body will be `f_(1)= mu_(s) mg` After the motion is stared , the friction will become kinetic So the force which is responsible for the increases in velocity of the block is
`F = (mu_(s) - mu_(s))mg = (0.8 - 0.6) xx 4 xx 10 = 8N`
`so a = (F)/(m) = (8)/(4) = 2ms^(-2)`