Question

car moving with a velocity of 72 kmph stops its engine just at the foot of a hill. if the car ascends a height of 12m, the energy lost in overcoming friction is $(g=10m/s^2)$

Answer 1

$v=72kmph=20m/s$

mass=$M$

Initial K.E$=K=\frac{1}{2}m{v}^2=200M$

Final KE=0

Work done by gravity $W_g=-Mgh=-120M$

Energy lost in overcoming friction= Initial energy$-$energy lost in overcoming gravity

$=200M-120M$

$=80M$