How about we bet our lives on this one? I’ll even let you be the one who decides who will win the bet knowing full well that you wont be able to decide rightfully. Here it comes: Lets consider body A and body B in evacuated space giving no resistance to their motion form unchangeable viewpoint. A is at rest. B is traveling with constant speed towards A. I bet I’ll bring Newton’s mechanics into contradiction with its self, viewing A and B before, at the time of and after the impact! What do you bet on? Before the impact neither A nor B is subjected to force because of Newton 1. At the time of the impact: A changes its speed from 0 to constant value. This change in time it takes exerts force on A. So A exits the impact with constant speed yet subjected to force. B changes its speed from constant value to 0. This change in time it takes exerts force on B. So B exits the impact at state of rest yet subjected to force. It is because of Newton 2 and definition of force as change of impulse in time. After the impact Newton 1 is impossible!