KE = ½mv2 P = mv Therefore, KE = ½(mv)2∕m = p2∕(2m) Considering the mass to be constant, if the momentum is increased by 20%, let the new momentum be P/ = P + 0.2P = 1.2P. New kinetic energy, KE/ = (P/)2/(2m) ⇒ KE/ = (1.2)2[P2∕(2m)] = 1.44KE ⇒ (KE/)/KE = 1.44 ⇒ (KE/ - KE)/KE = 0.44 ⇒ (KE/ - KE)/KE × 100% = 44%