Two low-friction carts with a combined mass of collide on a horizontal track
PHYSICS · Single correct · A Level · Physics · Mechanics and materials · Mechanics and materials
Problem
Two low-friction carts with a combined mass of 1.5kg collide on a horizontal track. During the 0.020s collision interval, the net external horizontal force on the system is 0.10N. Which statement most strongly supports treating the system’s total linear momentum as conserved during the collision?
(a) Because the external force acts horizontally, it cannot change the system’s horizontal momentum.
(b) The collision is so brief that the carts move essentially the same distance, so any external force does no net work and momentum is conserved.
(c) The impulse from the 0.10N external force over 0.020s is much smaller than the impulses the carts exert on one another during the collision.
(d) Since the internal forces are equal and opposite, they cancel, making the net force on the system zero at every instant.