A box with weight `10N` rests on a horizontal surface. A person pulls horizontally it with a force of `3N` and it does not move. To start its motion, a second person pulls it vertically upward. If `mu_(s)=0.5` and `mu_(k)=0.3`, then find the smallest vertical force for which the box starts moving.

Options

A. `0N`
B. `4N`
C. `10N`
D. `6N`

Answer

B

Explanation

To start motion `3=mu_(x)(10-F)`
`rArr3=0.5(10-F)rArr6=10-FrArrF=4N`