Explain the derivation of universal law …

Let two bodies one of mass m1 and other of m2 is moving with initial velocities u1 and u2 and final velocities v1 and v2 respectively. dt= short time interval of collision For 1st body , Initial momentum =pi=m1u1 Final momentum =pf=m2u2 A/Q Newtons second law of motion F directly proportional to Rate change of mometum F directly proportional to change in momentum ÷ Time taken. ( F directly proportional to m1v1-m1u1÷dt)-------(1) For 2nd body! Initial momentum =m2u2 Final momentum = m2v2 A/Q Newtons second law of motion F directly proportional to Rate change of mometum F directly proportional to change in momentum ÷ Time taken (-F directly proportional to m2v2-m2u2÷dt) (F directly proportional to - - - -(m2v2-m2u2÷dt))------(2) From (1)and(2) m1v1-m1u1÷dt =-( m2v2-m2u2)÷dt m1v1- m1u1= -m2v2+m2u2 m1u1 +m2u2=m1v1 +m2v2 HOPE THIS HELP!

Of which momentum, energy, mass