Question

Is momentum conserved in this process?

• A. The momentum of the rail car alone is conserved
• B. The momentum of the rail car+sand remaining within the car in conserved
• C. The momentum of the rail car+all of the sand, both inside and outside the rail car, is conserved
• D. None of the three previous systems have momentum conservation

Answer 1

The correct option is C The momentum of the rail car+all of the sand, both inside and outside the rail car, is conserved

Since there is no force in horizontal direction on rail car, it's momentum will be conserved. As the sand begins to pour down the mass of rail car decreases and it's speed increases.