Which simple machines are used in the tool or device

What does the term discrediting mean?

Chemical energy is a form of energy. a. heat b. kinetic c. potential d. electromagnetic

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.