Two identical low-friction pucks rest on a horizontal tabletop
PHYSICS · Multi-part · CBSE · Physics · Laws of Motion · Laws of Motion
Problem
Two identical low-friction pucks rest on a horizontal tabletop. Puck A is given a quick push so that it slides toward stationary Puck B and collides with it. The coefficient of kinetic friction between each puck and the table is μk=0.05. The collision itself lasts 0.015s, after which the pucks continue sliding across the surface.
(a) For the system consisting of only the two pucks, list every distinct force that acts on the system during the 0.015s collision interval. Classify each listed force as internal or external to the chosen system and state the physical object that exerts it.
(b) Using qualitative reasoning and the given numerical values, explain whether the vector linear momentum of the two-puck system is approximately conserved during the 0.015s collision. Include a comparison of the relative magnitudes of the relevant forces.
(c) The pucks continue to slide for several seconds after they separate. Suppose the system boundary is re-drawn to include the tabletop (and Earth attached to it) in addition to the two pucks. For this expanded system, discuss whether a conservation-of-momentum model can be applied over a time interval of several seconds following the collision. Justify your answer by referring to the forces that become internal or external under the new choice of system.