1. The problem statement, all variables and given/known data "A stream of sand moving at 4 m/s is directed horizontally eat against a wall at a rate of 120 kg per minute. If the sand falls vertically downward after impact, find the horizontal force exerted by the wall on the sand, and the horizontal force exerted by the sand on the wall". 2. Relevant equations ΣF = ma, W = mg, 3. The attempt at a solution I'm really lost on how to solve this problem. You aren't given the acceleration or the time that it took, so I can't work out the mass. I'm not sure what I'm missing but any help is appreciated, thanks.