This is the 2nd set of homework problems. These all come from Bloomfield's Student Supplement .

5.6. Firefighters are battling a fire in a tall apartment building. The water pressure in the adjacent fire hydrant is about 500,000 Pa above atmospheric pressure.

a. Some firefighters take their hose up the stairwell inside the building. What is the highest level at which they can expect water to flow out of their hose without additional pressure?

b. Firefighters on the ground begin to spray water upward from their hoses. The water enters the hose traveling slowly at 500,000 Pa above atmospheric pressure. How fast will the water be traveling when it leaves the nozzle at atmospheric pressure?

c. How high will the water in part b rise if the firefighters send it straight up?

d. To boost the water pressure, the firefighters send it sequentially through pumps in two fire engines. Each pump boosts the pressure by 500,000 Pa, for a total of 1,500,000 Pa above atmospheric pressure. How high will this water rise in hoses carried up the stairs inside the building?

6.8. You and your best friend live on the 58th floors of two adjacent high-rise apartment buildings. You have windows that face one another across an open courtyard. One day, the city turns off all the water to your friend's building. You decide to help your friend obtain water. You immediately buy 500 m of garden hose, enough to reach from either apartment to the ground at least two times.

a. Your first thought is to run water from the gardener's faucet, which is at street level in the courtyard, up to your friend's apartment. Although water runs briefly into the hose, it never reaches your friend's apartment. Why not?

b. You decide to obtain water from a faucet in your apartment. You run the hose out your window, down to the courtyard, and up to your friend's apartment. To your surprise, the hose bursts in the courtyard when you turn on the water. Why does the hose burst?

c. You patch the hose and decide not to let it droop down to the courtyard. With the hose running almost directly across the gap between windows, you turn on the faucet. What happens this time?

d. Water is flowing rapidly through all 500 m of hose as your friend fills a bathtub. To stop the flow, your friend suddenly makes a kink in the end of the hose. The pressure in the hose increases and the hose bursts. What produced this pressure surge?

e. As water flows out of the narrow split in the hose, it accelerates to a very high speed. What happens to its pressure as its speed increases?

7.6. Your room is particularly cold at night. Here are several things that you decide to do to make your room more comfortable.

a. You tape sheets of clear plastic across the windows of your room. Why do these plastic sheets make the room warmer?

b. You install curtains on the windows and draw them at night. How do the drawn curtains make your room warmer?

c. Your room has a high ceiling. You install a ceiling fan to push the air downward from the ceiling. Why does the fan make the air warmer near the floor?

d. You put a thick, down comforter or quilt on your bed. Describe in terms of heat flow how the comforter keeps you warm in bed.

e. You put an electric blanket on the bed. It uses electricity to make heat inside the blanket itself. How does this heat flow from the electric blanket to you?

8.8. When air in the atmosphere rises or falls it often experiences a change in temperature. Interesting examples of this behavior are the chinook winds in the Rocky Mountains and the foehns in the Alps.

a. When a wind containing moist air blows up the side of a tall mountain, its altitude increases and its pressure drops. What happens to this air's density?

b. Why does this rising air experiences a drop in temperature?

c. The air's dropping temperature causes its moisture to condense into rain while the air itself continues over the mountaintop without the moisture. As the moisture condenses from a gas into a liquid, it warms the air. Which portion of an air conditioner employs a similar process?

d. The warmed air then descends into the valley beyond the mountain and it warms up even more. The air reaching the valley is unusually hot and dry. Explain this additional warming during its descent.