A car and a bus are moving down a hill, the bus is 3X heavier than the car and the speed of the car is 3X faster than the bus. Compare their momentum and K.E.
Momentum is M*V
It is clearly the same for bus and car, since
M(bus)*V(bus) = 3*(1/3) M(car)*V(car)
= M(car)*V(car)
The kinetic energy of the car is three times that of the bus. I hope you see why.
K.E. = (1/2)*(momentum)*V
With momentum the same for both, the KE ratio is the V ratio.