Physics homework

132 Homework 4 Due Saturday Jan. 30

Read Chapter 13 through section 13-11 (we don’t do anything out of 12 or 13)

Chapter 13 Problems: (Not like you have to read ANY of Chapter 13 for these

exercises in F to Celsius or C to Kelvins. But in the interest of showing your

work, use the equation on page 356. And you should know how to go from C to

K, but I will review it.)

4,

Thermal Expansion Exercise 2: Suppose the concrete bridge over the BNSF tracks on the Cheney Spokane road (at Marshall) is 80.0m long. Use the data in Table 13-1 to calculate the

amount this bridge expands from a cold winter night (-20.0C is about as cold as it gets in a

typical year, and it might not even make that this year) to a hot summer day (41.0C). You might

observe the gap in the expansion joint to verify that it has at least a few cm of play.

Exercise 3: Pyrex is useful for cooking because you can subject it to sudden high temperatures

and it will not break. Look over Table 13-1 and you will see something notable about the value

for Pyrex that makes it resistant to thermal breaking. Explain.

Four for Ratio Reasoning with the ideal gas law: 23, 26, 32, [With ratio reasoning,

you can keep the original units for pressure and volume.]

Exercise 7: A methane bubble starts at the bottom of a lake (15.0 meters down) where the water temperature is 4.00C and rises to the surface where the water temperature is 22.0C (hey,

it’s summer at Rock Lake, and this is a reasonable temperature.) and the air pressure is 0.920

atmospheres. Assuming the gas is ideal and rises slowly enough that its temperature changes

exactly as the water does, find the factor by which the final volume is different than the initial.

(Final volume = f×initial volume.)

More Ideal Gas Laws:

31Modified[Suppose the air pressure outside is 9.20E4 Pa, as you might have in Cheney in the summer. Assume also a 1.50E3 cm3 volume for the tire. Find the number of moles of gas in the

tire at start, and then the new pressure at 38.0C (use 273.2K = 0.0C). Then find the number of

moles which must be released to make the gauge pressure 230. kPa.],

Molecular Speeds[These are all VERY short]: 44, 45, 46, 49

88 [This one tells you why any crack in the re-entry shield will result in vaporizing the vehicle.]