Question

The retarding acceleration of $4.9{\text{ms}}^{-2}$ due to frictional force stops the car of mass $400\text{kg}$ travelling on a road. The coefficient of friction between the tyre of the car and the road is

• A. $0.7$
• B. $0.5$
• C. $0.4$
• D. $0.3$

Answer 1

The correct option is B $0.5$

As we know, coefficient of friction $\mu =\frac{F}{N}$
Here we would take kinetic friction as the car will be sliding

$\Rightarrow \mu =\frac{ma}{mg}=\frac{a}{g}(a=4.9{\text{ms}}^{-2}\text{given})$
$\therefore \mu =\frac{4.9}{9.8}=0.5$