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 exernal force of magnitude `30 N` is applied applied parallel to the ground. The resultant force exernal by the ground on the block is `(g = 10 m//s^(2))`

Options

A. `40 N`
B. `30 N`
C. zero
D. `50 N`

Answer

D

Explanation

`N = mg = 40 N`
`mu N= 32 N`
Applied force `F = 30 N lt mu N`
Therefore friction force,
`f = F = 30 N`
:. Net connect force from ground on block
`= sqrt (N^(2) + f^(2)) = 50 N`