Thermodynamics and Fluid Mechanics Quiz for AP Physics B & C (page 2)
Are you getting ready to take the AP physics exam? Before you begin studying, find out what you know and you don't know with these four fundamental quizzes: Mechanics Quiz for AP Physics B & C , Thermodynamics and Fluid Mechanics Quiz for AP Physics B & C , Electricity and Magnetism Quiz for AP Physics B & C , and Waves, Optics, Atomic and Nuclear Physics Quiz for AP Physics B & C
It's okay if you didn't get every question on all of the fundamentals quizzes correct. The whole point of these quizzes is for you to determine where to focus your study.
It's a common mistake to "study" by doing 20 problems on a topic on which you are already comfortable. But that's not studying … that's a waste of time. You don't need to drill yourself on topics you already understand! It's also probably a mistake to attack what for you is the toughest concept in physics right before the exam. Virtually every student has that one chapter they just don't get, however hard they try. That's okay … (as long as it's only one chapter.)
These fundamentals quizzes can tell you exactly what you should and should not study. Did you give correct answers with full confidence in the correctness of your response? In that case, you're done with that topic. No more work is necessary. The place to focus your efforts is on the topics where either you gave wrong answers that you thought were right, or right answers that you weren't really sure about.
Here is the thermodynamics and fluid mechanics quiz.
- What is the equation for linear thermal expansion? What are the units for the coefficient of linear expansion?
- How do you determine the internal energy of a gas given the temperature of the gas? Define all variables in your equation.
- How do you determine the rms speed of molecules given the temperature of a gas? Define all variables in your equation.
- State the equation for the first law of thermodynamics. What does each variable stand for? What are the units of each term?
- Sketch two isotherms on the PV diagram below. Label which isotherm represents the higher temperature.
- Describe a situation in which heat is added to a gas, but the temperature of the gas does not increase.
- Imagine you are given a labeled P-V diagram for one mole of an ideal gas. Note that one of the following is a trick question!
- How do you use the graph to determine how much work is done on or by the gas?
- How do you use the graph to determine the change in the gas's internal energy?
- How do you use the graph to determine how much heat was added to or removed from the gas?
- What is the definition of the efficiency of an ideal heat engine? How does the efficiency of a real engine relate to the ideal efficiency?
- For the equation P = P0 + ρgh,
- for what kind of situation is the equation valid?
- what does P0 stand for (careful!)
- Write Bernoulli's equation.
- State Archimedes' principle in words by finishing the following sentence: "The buoyant force on an object in a fluid is equal to …
- For a flowing fluid, what quantity does Av represent, and why is this quantity the same everywhere in a flowing fluid?
- Write the alternate expression for mass which is useful when dealing with fluids of known density.
- ΔL = αLoΔTThe units of α can be figured out by solving for
- U = NkBT. Internal energy is 3/2 times the number of molecules in the gas times Boltzmann's constant (which is on the constant sheet) times the absolute temperature, in kelvins. Or, U = nRT is correct, too, because NkB = nR. (Capital N represents the number of molecules; small n represents the number of moles.)
- The isotherm labeled as "2" is at the higher temperature because it's farther from the origin.
- Let's put the initially room-temperature gas into a boiling water bath, adding heat. But let's also make the piston on the gas cylinder expand, so that the gas does work. By the first law of thermodynamics, if the gas does as much or more work than the heat added to it, then ΔU will be zero or negative, meaning the gas's temperature stayed the same or went down.
- (a) Find the area under the graph. (b) Use PV= nRT to find the temperature at each point; then, use U= nRT to find the internal energy at each point; then subtract to find ΔU. (c) You can NOT use the graph to determine heat added or removed. The only way to find Q is to find ΔU and W.
- For an ideal heat engine.
- This is valid for a static (not moving) column of fluid.
- P0 stands for pressure at the top of the fluid; not necessarily, but sometimes, atmospheric pressure.
- . … the weight of the fluid displaced.
- Av is the volume flow rate. Fluid can't be created or destroyed; so, unless there's a source or a sink of fluid, total volume flowing past one point in a second must push the same amount of total volume past another downstream point in the same time interval.
- mass = density · volume.
The units of length cancel, and we're left with 1/K or 1/°C. (Either kelvins or degrees Celsius are acceptable here because only a change in temperature appears in the equation, not an absolute temperature.)
kB is Boltzmann's constant, T is absolute temperature in kelvins, and m is the mass of each molecule in kilograms (NOT in amu!)
Change in internal energy is equal to (say it in rhythm, now) "heat added to, plus work done on" a gas. Each term is a form of energy, so has units of joules.
A real heat engine will have a smaller efficiency than this.
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