Collisions
There is also another use of Newton’s Second Law for collisions when we use it in combination with Newton’s Third Law
(Fby 2on 1 = - Fby 1on 2)
S Fx on 1 = Fexton 1 + Fby 2on 1 = D(m1vx1 )/Dt
S Fx on 2 = Fexton 2 + Fby 1on 2 = D(m2vx2 )/Dt.
If we add the left sides and add the right sides of the above two equations, we get the forces of collision canceling out!