Which object is in static equilibrium?

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.

For the car in the picture ,in which direction is the normal force? -into the screen -down -out of the screen -up

The discovery of the electron as a subatomic particle was a result of