Two boxes are connected by a string. The first box has a mass of 4.2 kg and the second 2.8 kg. A string attached to the first box pulls horizontally with a force of
7.5 N. Calculate the tension in the second string if the force of friction on the first
box is 2.0 N and the force of friction on the second is 1.6 N.

Arigid tank is divided into two equal parts by a partition. one part of the tank contains 3 kg of compressed liquid water at 400 kpa and 60°c while the other part is evacuated. the partition is now removed, and the water expands to fill the entire tank. determine the entropy change of water during this process, if the final pressure in the tank is 40 kpa. use steam tables.