1. The problem statement, all variables and given/known data A solid object of 6kg was moving at a constant speed of 10m/s towards a man who try to stop it. If the man stopped the train in 30 seconds, find the force F that the man exerted on the object. 3. The attempt at a solution The only force acting on the object is the man's force so : ma=-F, this means that : v(t)=v(0)-F t /m. We know that v(30)=0, wich means that : F= m*v(0)/30 = 2. Is my solution correct ? (I don't have anyone to ask him so I'm asking you).