Question

A wedge is moving rightwards on which a block of mass `10kg` is placed on it. Friction coefficient between the wedge and the block is `0.8.[` takes `g=10m//s^(2)]`. Select correct alternative `(s)` among the following options.

A. If wedge is moving with constant velocity then friction acting on block is `64N`.
B. If wedge is moving with constant velocity then acceleration of block is zero.
C. If wedge is moving with `vec(a)=2(hat(i))m//s^(2)` then friction acting on block is `44N`
D. If wedge is moving with `vec(a)=10(hat(i))m//s^(2)` then friction is `20N`, downward on the wedge along the inclined.

Answer 1

Correct Answer - C::D
`(A,B)` If moving with constant velocity then `a=0` so friction available `=mumgcostheta`
`=(0.8)(10)(10)(4//5)=64N`.

but `mgsintheta=60N`
so required friction is `60N`.
So net force is zero .
`(C ) a=2hat (i) f=mg sin 37^(#)-m a cos 37^(@)=44N`
`(D) f=mg sin 37^(@)-ma cos 37^(@)=-20N`