# A bus and a car that are moving have the same kinetic energy. Which has a greater velocity?

*print*Print*list*Cite

### 1 Answer

The kinetic energy of a body is given as K.E. = (1/2)*m*v^2 J, where m is the mass in kilogram and v is the velocity in m/s.

If two objects have the same kinetic energy, but their mass is different the velocity also has to be different. If the first body has a mass M1 and is moving at a velocity V1 and the second has a mass M2 and is moving at a velocity V2, an equal kinetic energy implies M1*V1^2 = M2*V2^2

Here, the car and the bus have the same kinetic energy; but the mass of a bus is larger than that of the car. The velocity of the car would have to be greater than that of the bus. The formal relation between the velocity of the bus Vb and that that of the car Vc is: (Vb/Vc) = sqrt(Mc/Mb), where Mc is the mass of the car and Mb is the mass of the bus.

**Sources:**