Rocket Science on Barges

Two long barges are moving in the same direction in still water, one with a speed of 10 km/h and the other with a speed of 20 km/h. While they are passing each other, coal is shoveled from the slower to the faster one at a rate of 1000 kg/min.

How much additional force must be provided by the driving engines of (a) the faster barge and (b) the slower 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 masses of the barges. Choose the answer that equals the sum of answers to (a) and (b).

Problem credit: Fundamentals of Physics Extended, 9th Edition

×