HVAC · Practice-Exam-2 · Problem 54PDFSolution in PDF ↓
HVAC · Practice-Exam-2 · Problem 54
Problem & Solution
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Topic: Practice Exam #2 — A pressurized tank contains air at 300 psi A.
Method: What is the mock number of air entering the atmosphere through a hole in the tank?
Formula reference: formula that's used to make the table that we just used in the first option.
Key values: 300 psi, 14.7 psi
Reference: table that will allow us to look up the mock number directly
✅ Answer: B
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Student questions asked in live office hours about this problem
OH 119 · April 28, 2026
Q: Where in the reference handbook is the equation to solve directly for Mach number from the stagnation pressure ratio P₀/P?
A: There is no separate Mach number equation in the handbook — it is an algebraic rearrangement of the listed P₀/P stagnation equation. You raise both sides to the power (k−1)/k, subtract 1, multiply by 2/(k−1), and take the square root to isolate M. In exam conditions you can also work numerically: compute the pressure ratio, then manipulate it step-by-step on the calculator without solving for M symbolically first.