Member has been reminded to provide typed text instead of barely readable pictures.
Freight car and hopper*
An empty freight car of mass M starts from rest under an applied force F. At the same time, sand begins to run into the car at steady rate b from a hopper at rest along the track.
Find the speed when a mass of sand m has been transferred.
The Attempt at a Solution
The solution answer has an extra b*t in the denominator and + answer. Where is the flaw in my method? Now I understand this can be done shorter using impulse and exact values but I prefer the more general approach and deduce specific cases at the end. Thanks