a uniform metal rod of length 80cm is suspended by a string at a point 22cm from the end. When a weight of 15N hangs from a point 13cm from the end, the rod balances in a horizontal position as shown in the diagram. How far from the string is the point where the weight of the metal rod acts

An insulated 40 ft^3 rigid tank contains air at 50 psia and 120°f. a valve connected to the tank is now opened, and air is allowed to escape until the pressure inside drops to 25 psia. the air temperature during this process is kept constant by an electric resistance heater placed in the tank. determine the electrical work done during this process.