In the figure below, two long barges are moving in the same direction in still w
ID: 2093635 • Letter: I
Question
In the figure below, two long barges are moving in the same direction in still water, one with a speed of10km/h and the other with a speed of20km/h. While they are passing each other, coal is shoveled from the slower to the faster one at a rate of900kg/min. How much additional force must be provided by the driving engines of each barge if neither is to change speed? Assume that the shoveling is always perfectly sideways and that the frictional forces between the barges and the water do not depend on the weight of the barges.
Explanation / Answer
The fast one becomes 1000 kg heavier in one minute. So the momentum to preserve is 10km/h * 1000 kg in one minute.F = (10 km.900kg/h)/(1/60)h =540000km.kg/h^2 = 46,3 kg.m/s^2 = 46,3N
For the slow one, it's twice that