A Railroad Car of Mass 12,000 Kg Is Moving Horizontally

Multiple Choice

A railroad car of mass 12,000 kg is moving horizontally at 10 m/s. Suddenly it starts to rain, and water accumulates in the railroad car. Which of the following is true?

A) The railroad car slows down because the linear momentum of the rain + car system is conserved.
B) The railroad car continues to move at 10 m/s because the rain is falling vertically while the car is moving in a horizontal plane.
C) The railroad car continues to move at 10 m/s because the linear momentum of the rain + car system is conserved.
D) The railroad car continues to move at 10 m/s because the total energy of the rain + car system is conserved.
E) The railroad car speeds up because the potential energy of the rain is converted into kinetic energy for the car.