Question

Consider a car moving on a straight road with a speed of $100m/s$. The minimum distance at which car can be stopped is (${\mu }_k=0.5$)

• A. $800m$
• B. $1000m$
• C. $100m$
• D. $400m$

Answer 1

The correct option is B $1000m$

Given: Initial velocity= 100 m/s

Final velocity=0

Coefficient of friction= ${\mu }_k=0.5$

Solution: According to third equation of motion,

$v^2-u^2=2as$

where v is the final velocity,

u is the initial velocity,

a denotes the acceleration and

s is the displacement.

Also, $a=\mu g$ ($g=10m/s^2$)

Substituting the values we get,

${\left(0\right)}^2-{\left(100\right)}^2=-2(0.5\times 10)s$

On solving we get,

$s=1000m$

Hence, the correct option is (B).