Two identical pucks slide on a frictionless horizontal surface
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Linear Momentum · Linear Momentum
Problem
Two identical pucks slide on a frictionless horizontal surface. Puck P travels due east with speed v and collides head-on with identical puck Q, which is initially at rest. The pucks stick together and move off as a single object. Which statement best explains why the total kinetic energy after the collision is less than before?
(a) Because the two pucks stick together, the total mass of the system doubles; with a larger mass but the same momentum, the kinetic energy must be smaller.
(b) Some kinetic energy is lost when friction between the pucks and the tabletop does negative work on the system during the brief impact.
(c) Some of the initial kinetic energy is transformed into internal energy within the combined puck, primarily because the pucks deform during the impact.
(d) Part of the translational kinetic energy is converted into rotational kinetic energy of the joined pucks, so the translational kinetic energy after the collision is lower.