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## Homework Statement

A Freight Car of Mass M contains a mass of sand m. At t=0, a constant horizontal force i applied in the direction of rolling, and at the same time a port in the bottom is opened to let the sand flow out at a constant rate dm/dt. Find the speed of the freight care when all the sand is gone. Assume the car is at rest at t=0

## Homework Equations

F= ma

mv = mv - conservation of momentum?

## The Attempt at a Solution

If there were no sand leaking from the bottom of the train, then the train would be accelerating at a constant acceleration because F= (M+m)a and the masses would be constant. However, the mass is changing, so the acceleration will be increasing over time. I'm just not sure how I can put these into a mathematical answer