Calculating Force for Moving Railroad Car

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To calculate the force needed to keep a railroad car moving at a constant speed of 4.50 m/s while grain is added at a rate of 680 kg/min, the momentum change must be determined. The relevant equations include momentum (p = mv) and force (F = dp/dt). Since friction is negligible, the force required is directly related to the rate of change of momentum as the mass of the car increases due to the grain. The key is to convert the grain drop rate into consistent units for accurate calculations. The solution hinges on understanding how the added mass affects the momentum and, consequently, the force needed to maintain constant velocity.
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Homework Statement



A railroad car moves under a grain elevator at a constant speed of 4.50 m/s. Grain drops into the car at the rate of 680 kg/min. What is the magnitude of the force needed to keep the car moving at constant speed if friction is negligible?

Homework Equations



p = mv
F = dp/dt

The Attempt at a Solution



?
 
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OK. So what is the Δmv?
 

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