Question

Calculate the work required to be done to stop a car of $1500kg$ moving at a velocity of $72kmph$?

Answer 1

Kinetic energy, $E_k=\frac{1}{2}m{v}^2$
where, mass of car, $m=1500kg$
velocity of car, $v=72kmph=\frac{72\times 5}{18}m{s}^{-1}=\frac{20}{1}m{s}^{-1}$
$\therefore E_k=\frac{1}{2}\times 1500\times (20{)}^2=30\times {10}^{4}J$
Hence, $30\times {10}^{4}J$ of work is required to stop the car.