Calculate the kinetic energy of a car of mass 750 kg moving with a velocity of 54 km. Find the new kinetic energy of the car, if a passenger of mass 50 kg sits in the car.

Given, mass, m = 750 kg, velocity, v = 54 kmh

= 54 X5/18 ms = 15 m

Kinetic energy, KE = 1/2 m ${{v}^{2}}$

=> KE = 1/2 x 750 x 15 x 15 = 84375 J

If a passenger of mass 50 kg sits in the car, then total mass becomes (750 + 50) kg, i.e. 800 kg

.-. New KE = 1/2 x800x15 x 15 =90000J