# Could you solve this?

## A small box resting on one edge of the table is struck in such a way that it slides off the other edge, 1m away, after 2 seconds. The coeeficient of kinetic friction between the box and the table a. must be less than 0.05 b. must be exactly zero c. must be more than 0.05 d. must be exactly 0.05

Oct 3, 2016

The answer is (a) Coefficient of kinetic friction must be less than 0.05

#### Explanation:

For limiting case,

 F = μ_s * m g

now using,

$S = \frac{1}{2} a {t}^{2}$

$\implies 1 = \frac{1}{2} \cdot a \cdot {2}^{2}$

$\implies 1 = 2 \cdot a$

$\implies a = \frac{1}{2} \frac{m}{s} ^ 2$

$\implies a = 0.5 \frac{m}{s} ^ 2$

For sliding friction,

$F > {\mu}_{k} \cdot m g$

$\implies m a > {\mu}_{k} \cdot m g$

$\implies {\mu}_{k} < \frac{a}{g}$

taking $g = 10 \frac{m}{s} ^ 2$

$\implies {\mu}_{k} < \frac{0.5}{10}$

$\implies {\mu}_{k} < 0.05$