 Photo via : Defence Images | The problems for the afternoon section in the NCEES "Sample Questions + Solutions" book are numbered 501 through 540. In this post we provide an analysis of Problem 503 of the Thermal and Fluid Systems depth (PM) section. Description: The statement for Problem 503 provides the ambient temperature and Mach number for a flying airplane. You are asked to calculate the airplane's velocity. |
| Analysis of Problem 503: This is a "slam dunk" problem as long as you are aware that the speed of sound is the square root of the product of the particular gas constant, the specific heat ratio, and the absolute temperature. This relationship between speed of sound in an ideal gas and the temperature of the gas is in every Fluid Mechanics and Thermodynamics textbook. To test your understanding of this subject, consider the following sample problem, which is just slightly more challenging than problem 503. This sample problem is a variant of an end-of-chapter homework problem from "Fundamentals of Fluid Mechanics" 6th edition, by Munson, et al. Thermal and Fluids Depth (PM) Exam Sample Problem #3 A military jet flies at a speed of 495 miles/hour at an altitude of 49,000 feet. A commercial airplane is flying at the same Mach number as the military jet but at an altitude of 27,000 feet. A plot showing the variation of temperature with altitude in the atmosphere is provided for your potential use.  |
| The speed (ft/s) of the commercial jet is most nearly: (A) 515 (B) 726 (C) 757 (D) 795 You may download the solution from the link below. Have questions? Need help with this problem? Then leave a comment below! 
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