Question

A car weighing 1400 kg is moving at a speed of 54 km/h up a hill when the motor stops. If it is just able to reach the destination which is at a height of 10 m above the point, calculate the work done against friction (negative of the work done by the friction).

Answer 1

$m=1400kg,$

$v=54km/h=15m/sec,$

$h=10m$

Work done =(total K.E.)-total P.E

$=\left(\frac{1}{2}\right)m{v}^2-mgh$

$=\frac{1}{2}\times 1400\times (15{)}^2-1400\times 9.8\times 10$

$=+157500-137200=20300J$

So, work done against friction,

$W_1=20300J$