I am a CIE A Level student and the following question is of 1st year undergraduate level. A bag containing a mass M of sand is suspended from a hook on the arm of a balance at a height h above the balance pan. At a time t=0, the sand starts to pour from a hole at the bottom of the bagm falling onto the pan beneath, and continues at a constant rate r (mass/unit time) until the bag is empty. i. Find the mass required on the other pan to maintain balance under steady conditions when a continuous stream of sand is falling from the bag (a simple balance with equal arms is envisaged). ii. Show graphically the variation with time of the mass required to maintain balance throughout the experiment, indicating by suitable labelling the quantities involved. Assume ideal conditions, under which air resistance, balance inertian and damping effects may be ignored. My working: When we consider the pouring of sand from a height h above the pan, there exists 3 phases: the falling sand yet to reach the pan; the steady stream of sand whose momentum is destroyed upon reaching the pan and the final stage when the steady stream of sand reduces to zero when all of the sand in the bag is depleted. So for the "mass required on the other pan to maintain balance under steady conditions when a continuous stream of sand is falling from the bag", I tried starting from the conservation of energy gh = 0.5 v^2. Since the height is yet to be found, I couldn't use the impulsive force on destroying of momentum too. I apologise for not having complex mathematical workings to present. please help. Thank you.