Question

Two frictionless pucks are connected by a rubber band.One of the pucks is projected across an air table, the rubber band tightens, and the second puck follows--in an apparantly randm way---the first puck. The center of mass of this two-particle system is located.

• A. at a fixed distance from one of the pucks
• B. usually ,but not always , between the two pucks.
• C. at a distance from one of the pucks that is a fixed ratio to the distance between the two pucks.
• D. sometimes closer to one puck and sometimes closer to the other.

Answer 1

The correct option is C at a distance from one of the pucks that is a fixed ratio to the distance between the two pucks.

In the effect of internal forces in a system, Center of mass doesm't change i.e its position remains fixed. Thus for a two particle system :

distance of com from M2 is a fixed ratio of $$\frac{m1}{m1+M2}$$