An Open Freight Car Rolls Friction Free Along a Horizontal

Multiple Choice

An open freight car rolls friction free along a horizontal track in a pouring rain that falls vertically. As water accumulates in the car, the car's speed

A) increases.
B) decreases.
C) remains the same.
This is best explained by the principle of
D) inertia.
E) momentum conservation.
F) energy conservation.
G) Newton's 2nd law.