text: help on physics question-newton's 3rd law? question:  suppose two people, one having 3x the mass of the other, pull on opposite sides of a 20 meter rope while on frictionless ice. after a brief time, they meet. the more massive person slides a distance of   a) 4m b) 5m c) 6m d) 7m  please explain how you get the answer cause i don't know what to do!! b) why there are four masses here 1 small guy + 3 big guy = 4.  divide 4 into 20, you get 5.  but that is only half the answer.  the big guy's mass is an anchor for the small guy.  so every time the big guy pulls he just pulling the small guy closer and every time the small guy pulls he is moving closer in a ratio of 3 to 1.  so the big guy only moves 5m and the small guy move 15m.