The kinetic energy of a body decreases by 36%. The decrease in its momentum is

P=2 mE    ∴P∝EIn given problem K.E. becomes 64% of the original value.P2P1=E2E1=64E100E=0.8⇒P2=0.8 P∴P2=80% of the original value.i.e. decrease in momentum is 20%.