A one kilogram textbook drops from a one-meter high table in a room at 250C temperature. Find the change in entropy in the universe. Now, two identical ideal oxygen gases with the same pressure P=1 atm and the same number of particles N = 1022, but di erent temperature T1 = 300C and T2 = 400C, are con ned in two vessels, of volume V1 = 1 liter and V2 = 2 liter which are then connected. Find the change in entropy after the system has reached equilibrium.