Question

A car is moving at a speed of $72km/hr$ on a road having $2\%$ upward gradient. The driver applies brakes when he sees an obstruction. If his reaction time is $1.5\text{seconds}$, assuming that the coefficient of friction between the pavement and tyre as $0.15$, calculate the distance traversed before the car finally stops

• A. $24m$
• B. $150m$
• C. $1056m$
• D. $324m$

Answer 1

The correct option is B $150m$

$v=\frac{5}{18}\times 72=20m/s$
$S=vt+\frac{v^2}{2g(f+n\%)}$
$=20\times 1.5+\frac{{20}^2}{2\times 9.81(0.15+0.02)}$
$=150m$