1. The problem statement, all variables and given/known data An empty freight car of mass M starts moving from rest with a constant applied force F0. At the same time, coal runs into the car at steady rate b from a hopper above the car at rest along the track. Calculate the velocity of the car as a function of time. GIVEN: M = 1400 kg; F0 = 42000 N; b = 150 kg/s; t = 6.5 s. 2. Relevant equations I have a problem setting up conservation of momentum problems; I was wondering if there are some basic steps or factors to always look at, and help me understand the anatomy of them. 3. The attempt at a solution I tried treating this like a rocket ship problem- Fexternal = F0 = d(mv)/dt F0*dt = d(mv) --> F0 = v*dM/dt + M*dv/dt = v*b + M*dv/dt to differentiate--> F0 - v*b = M*dv/dt --> (1/m)dt = (1/b)(1/F0/b - v)*dv V(t) = [F0/b]*[1-e-b*t/m] And plugging in I get 140.45 m/s which is not correct. will someone help me understand the anatomy of the conservation of momentum, any helpful links are also appreciated. Thanks!