Question

A car is accelerating on a horizontal road with acceleration = 20 $m/s^2$. A box that is placed inside the car, of mass m = 10 kg is put in contact with the vertical wall as shown. The friction coefficient between the box and the wall is $\mu$ = 0.6, then which one is true?

• A. The acceleration (with respect to ground ) of the box will be 20 $m/se{c}^2$
• B. The friction force acting on the box will be 100 N
• C. The contact force between the vertical wall and the box will be $100\sqrt{5}$ N
• D. The net contact force between the vertical wall and the box is only of electromagnetic in nature.

Answer 1

The correct option is B The friction force acting on the box will be 100 N

$N=ma$
$=10\times 20$
$N=200$
friction =$\mu N$
$0.6\times 200$
$=120N$
$mg=10\times 10=100$
so, $f>mg$, so friction will balance $mg$ so block do not fall down.