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Homework #2: Due Friday September 5 by 5:30pm
Note: As with all homework and test questions, you must show clearly how you obtained your answer. An answer alone is not sufficient, and even a correct number without adequate supporting work will receive zero credit.
That's all for homework #2.
- Estimate the number of air molecules in (a) a beach ball under a pressure of 1.5 atmosphere, and (b) your car (or a family car). In each case clearly state the dimensions that you are using.
- problem 1.12. Here you are solving for V/N. Assume a pressure of 1.0 atm.
- problem 1.14. Recall that 1 a.m.u=1.6605x10-27kg.
- problem 1.24. Assume lead behaves as the solid pictured in Figure 1.6.
- Let's let the heat energy kT do something useful such as "freeze out" and become an electron of mass m=9.11x10-31kg. Find the temperature equivalent to the mass-energy of an electron. Hint: Einstein taught us that mass is solid energy, and has an energy of mc2. And yes, as we shall see later, such temperatures existed near the beginning of the universe.
- Assuming the average density of the subsurface is a constant 2,700 kg/m3 find the total pressure at a depth below the surface of 35.0 meters. Assume the pressure at the surface is 0.94atm (careful of your units here!).
- Consider the pressure gradient equation with a constant density ρ=1.27kg/m3, but with a gravitational acceleration that varies with height z as g=GM/z2. Here, G=6.67x10-11Nm2/kg2, and M=5.98x1024kg is Earth's mass.
(a) As we did in class, find the general expression for the difference in pressure Pf-Pi between the two heights z1 and z2.
(b) Find the final pressure at a height above sea level of 560m, assuming P1=1.00atm, and Earth's radius is at sea level is 6,370.0km.
Note: There are sooooo many homework problems that could be assigned. However, you have other classes and sometimes insist upon sleeping (to your great folly). Thus you should always ask yourself "How might this problem's concept appear in another context?" The ability to generalize what you know is the goal.