Question

a bus and a car have same kinetic energy . which of the two is moving fast ? explain

Answer 1

As KE of a body is given by:
KE =(1/2)×m×v^2
(where m is mass and v is velocity of the body)
=> v=√ [2(KE )/m].......(1)
=> v is inversely proportional to √m .meaning that if we increase mass of body then to maintain a constant KE its velocity is decreased .
As mass of car is less than that of bus but both are having same KE.then, obviously car is moving faster than the bus.
ALTERNATIVELY:
you can suppose that velocity of car is v and velocity of bus is u And mass of car is m and that if the bus is M.
using equation (1),
v= √ [2(KE )/m]..........(2)
u= √ [2(KE )/M]...........(3)
dividing equation (2) by (3) we get,
v/u=√(M/m)>1. (as M is greater than m).
=> v>u.

Answer 2

both car and bus moving with same speed because its kinetic energy is same
kinetic energy =the energy possesed by a body by virtue of its motion