A block `A` of mass `4 kg` is kept on ground. The coefficient of friction between the block and the ground is `0.8`. The external force of magnitude `30 N` is applied parallel to the ground. The resultant force exerted by the ground on the block is `(g = 10 m//s^(2))` a) 40 N b) 30 N c) zero d) 50 N

Options

A. 40N
B. 30N
C. 0N
D. 50N

Answer

D

Explanation

N=mg=40
`(f_(s))_(max)=muN=(0.8) (40)=32`
`f_(S)=ext` force =30
`R^(2)=N^(2)+f_(s)^(2)=(50)^(2)`
`:. R=50 Nt`.