Question

A horizontal force of F N is acting on a 5 kg box, the box is sliding to the right and $v=10-2t$, coefficient of friction between the box & the floor is 0.1, then

• A. frictional force is towards right
• B. F < 5 N
• C. F may be greater than 5 N
• D. frictional force is zero

Answer 1

The correct option is B F < 5 N

$f_{kinetic}={\mu }_{k}N$

Since the block is retarding, net force must be towards left
$F-{\mu }_{k}N<0$
$F<{\mu }_{k}N$
$F<0.1\times 50$
$F<5$ N