Question

Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h?

Answer 1

Initial velocity of the car $u =$ $60 \ km/h$
$u = \frac {60×1000}{60×60}$

$u= \frac {50}{3}\ ms^{-1}$
Final velocity $v = 0$ (object has to be stopped)
Initial kinetic energy $= \frac 12×m×v^2$

$KE=\frac 12×1500×(\frac {50}{3})^2$

$KE = \frac {1500 \times 2500 \ }{2 \times 9}$
$KE= 208333.30\ J$
Final kinetic energy $= \frac 12×1500×0 = 0$
Therefore,
Work done = change in kinetic energy = $208333.30-0 = 208333.30\ J$