A block of mass `5 kg` is (i) pushed in case (A) and (ii) pulled in case (B), by a force `F=20 N`, making an angle of `30^(@)` with the horizontal, as shown in the figures. The coefficient of friction between the block and floor is `mu = 0.2`. The difference between the accelerattion of the block, in case (B) and case (A) will be : `(g = 10 ms^(-2))`.
.

Options

A. `0ms^(-2)`
B. `3.2ms^(-2)`
C. `0.4ms^(-1)`
D. `0.8 ms^(-1)`

Answer

D

Explanation

`(A)" "(B)`
`f_(1)=mu(mg+F sin theta)" "f_(2)=mu(mg-f sin theta )`
`a_(1)=(F.cos 30^(@)-f_(1))/m" "a_(2)(Fcos 30^(2)-f_(2))/m`
`a_(1)=(Fcos theta-mu mg -mu F sin theta)/m" a_(2)=(Fcos mumg+muFsin theta)/m`
`a_(2)-a_(1)=(2muF sin theta)/m" =(2xx0.2xx20xx1)/(5xx2)=0.8m//s^(2)`