Question

A body of mass $2kg$ is moving on a rough horizontal surface with an acceleration of $5m{s}^{-2}$ and when the horizontal force is doubled, it gets an acceleration of $18m{s}^{-2}$. Then the coefficient of friction between the body and the horizontal surface is : (assume $g=10m{s}^{-2}$)

• A. $0.2$
• B. $0.8$
• C. $-0.4$
• D. $0.6$

Answer 1

The correct option is B $0.8$

$m=10kg$
when $a_1=5m{s}^{-2}$
$R=mg$
${\mu }_1=\frac{ma}{mg}=\frac{5}{10}=0.2$
when $a_2=18m{s}^{-2}$
${\mu }_2=\frac{18}{10}=1.8$