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So, I know the "correct" answer to this problem, but it makes no sense to me at all. Why is the following the case?
A railroad hopper car has mass 40,000 kg when empty and contains 50,000 kg of coal. As it coasts along the track at 4 m/s the hopper opens and steadily releases all the coal onto a platform below the rails over a period of 4 s.
How fast does the car travel after all the coal is dumped?
Momentum = Mass x Velocity
40,000+ 50,000 = 90,000
90,000 x 4 = 360,000
360,000 / 40,000 = 9 m/s.
This seems simple and obvious, yet the computer insists that the correct answer is 4 m/s. Why would this ever be...?
Homework Statement
A railroad hopper car has mass 40,000 kg when empty and contains 50,000 kg of coal. As it coasts along the track at 4 m/s the hopper opens and steadily releases all the coal onto a platform below the rails over a period of 4 s.
How fast does the car travel after all the coal is dumped?
Homework Equations
Momentum = Mass x Velocity
The Attempt at a Solution
40,000+ 50,000 = 90,000
90,000 x 4 = 360,000
360,000 / 40,000 = 9 m/s.
This seems simple and obvious, yet the computer insists that the correct answer is 4 m/s. Why would this ever be...?