Answer :
I go to a British school so I'm going to assume momentum = kinetic energy. Not sure if this is what you learnt in class.
KE = 0.5 x mass x velocity^2
KE = 0.5 x 50 x 10^2
KE = 2500 Joules
KE = 0.5 x mass x velocity^2
KE = 0.5 x 50 x 10^2
KE = 2500 Joules