8. In the figure, two long barges are moving in the same direction in still water, one with a speed of km/h and the other with a speed of 24 km/h. While they are passing each other, coal is shoveled from the slower to the faster one at a rate of 710 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 mass of the barges.
9. The figure shows a uniform square plate of edge length 6d = m from which a square piece of edge length 2d has been removed. What are (a) the x coordinate and (b) the ycoordinate of the center of mass of the remaining piece?