Final answer:
When steam enters a nozzle, the pressure in the nozzle is close to atmospheric pressure. The pressure in the hose is greater than in the nozzle due to the increased speed in the nozzle. The water stream exerts a large force on anything it strikes.
Step-by-step explanation:
When steam enters a nozzle at 400 and 800 kPa, the pressure in the nozzle is very close to atmospheric pressure because the water exits into the atmosphere without changes in its conditions. This is because the pressure in the hose is greater than in the nozzle due to the increased speed in the nozzle.
The water stream exerts a large force on anything it strikes by virtue of its kinetic energy, and the pressure becomes equal to atmospheric pressure once it emerges into the air.