Question

If a body of mass 3kg has velocity 5m/s what is the kinetic energy

Answer 1

kinetic energy =1/2mv^2
m=3 kg
v=5 m/s
K.E =1/2×3×25=75/2=37.5 J

Answer 2

The collision being inelastic implies the both masses clump together to one ie the total mass after collision is (40+60)=100kg.According to conservation of momentum applied to both the bodies under collision the eqn is

40×4+60×2=100×v=>280=100v=>v=280/100

=2.8m/s.So the energy of the system before collision is (1/2)40×4²+(1/2)60×2²=320+120

=440J.But energy after collision=(1/2)100×2.8²

=392J.So energy loss =440–392=48J.ans.