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Slay the P.E.

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Slay the P.E. last won the day on October 7 2018

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About Slay the P.E.

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    Principal in Charge

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    Prospect Heights, IL
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    Mechanical Engineering Exam Prep

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  1. Oh, OK then. At this point there's not much else you can do. Have you checked out the "practice problem of the week" thread? There's like 8 or 9 problems there as well as lively discussion among EB users on the solutions and techniques. Highly recommended:
  2. I’m grateful that you’ve tried our exam and that you’ve found it useful. I assume you’ve also worked the NCEES practice exam. That being said, I don’t think I’ve ever encountered anyone who only used those two resources for their exam prep. There’s a lot more you can do; although at this point time is quite precious. At a minimum, I would recommend getting the practice exam from Engineering Pro Guides to get another fresh set of problems: I would also shamelessly plug our practice problems books available from our website, but like I said, probably not worth spending the money on the set of books if you only have 3 days to review the 300+ questions in them. ¯\_(ツ)_/¯
  3. The energy balance for this configuration is always power = mass flow rate (change in enthalpy). It's just a matter of how you want to calculate the change in enthalpy. The simplest way is to assume constant specific heat so that (change in enthalpy) = Cp (change in temperature). A little more accuracy is obtained if instead of assuming constant Cp you use the air tables which are calculated with variable Cp (this is what they did in the solution). At this point people always ask "when do I use constant Cp and when do I use tables?". With constant Cp the results obtained are reasonably accurate if the temperature interval is not very large. But, what is "very large"? In this problem as a first pass we calculate the discharge temperature assuming constant Cp to be about 1330 R. The inlet was 530 R so the temperature range was about 800R, yet the difference in the result (45810 vs 46309) is about 1%. If the temperature difference is like 1000R I would start to be more careful. The other criterion is if the problem statement explicitly asks you to use the air tables (e.g. problem 535 in the NCEES sample exam) This also depends on the gas. As you can see from the figure below, you can almost blindly use constant Cp for of monatomic gases such as argon, neon, and helium, but for something like CO2 you would have to be careful with what value of Cp you're going to pick and use as a constant in your calculations.
  4. In a sense, these boards are like a study group. You can post here any questions that arise during your study and the community typically answers very quickly. Also, if you're looking for additional practice problems, check out this thread:
  5. Correct, (C) yes, all problems in the thread have been answered and thoroughly discussed.
  6. Correct. The normal stress is due to two sources: the axial force normal to the section, and the bending moment due to the external load.
  7. Absolutely the best advice for that question. @Aurora09, if you do this you will see that P2 - P1 = pgHf (where Hf is frictional head loss), is obtained for z1 = z2 and d1 = d2 where d is the pipe ID. Extended Bernoulli can also address your other questions regarding sloped and vertical pipes.
  8. Friendly reminder that this thread is still relevant. Cheers, and good luck
  9. Thanks for the shout out. We’re glad to have been of service in your studies. Congrats!!!
  10. Thanks!! Much appreciated. Congratulations!!
  11. Thank you for creating this thread. 😊
  12. If coach woulda put me in 4th quarter we would’ve been state champions. No doubt.
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