Two identical carts are initially held together at rest on a frictionless horizontal…
PHYSICS · Single correct · AP · Physics 1: Algebra-based · Force and Translational Dynamics · Force and Translational Dynamics
Problem
Two identical carts are initially held together at rest on a frictionless horizontal track by a string attached to a compressed spring between them. When the string is cut, the spring pushes the carts apart so they move in opposite directions. Neglect external horizontal forces. Which statement best describes the motion of the system’s center of mass immediately after the string is cut?
(a) The center of mass accelerates toward the cart that moves faster because that cart has greater kinetic energy.
(b) The center of mass oscillates back and forth since the spring force on each cart changes during the push.
(c) The center of mass remains at rest because there is no external horizontal force acting on the system.
(d) The center of mass moves opposite the direction of the cart that gains less speed, as equal internal forces give the carts unequal accelerations.