In this article, (and video above), I solve a continuity equation question similar to one you might encounter on the mechanical section of the FE Exam.
Which of the statements is true concerning the following continuity equation?
p is density, u is velocity in the x direction, v is velocity in the y direction, and w is velocity in the z direction.
(A) It is valid only for incompressible flow.
(B) It is valid only for steady flow.
(C) It is derived from the principle of conservation of mass.
(D) It is derived from the principle of conservation of energy.
In essence, the continuity equation states that the mass flux entering a control volume is equal to the mass flux leaving the control volume plus the rate of accumulation of mass within the control volume. It is derived from the principle of conservation of mass. It is valid for all real and ideal fluids, and for all types of fluid flow. However, there are some things you need to be careful about when answering this question, which I review in the video at the top of this post.
The correct answer is C. It is derived from the principle of conservation of mass.
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I hope you found this week’s engineering ethics question helpful. In upcoming articles, I will answer more FE Exam questions and run through more practice problems. We publish videos bi-weekly on our Pass the FE Exam YouTube Channel. Be sure to visit our page here and click the subscribe button as you’ll get expert tips and tricks – to ensure your best success – that you can’t get anywhere else. Believe me, you won’t want to miss a single video.
Lastly, I encourage you to ask questions in the comments of the videos or here on this page and I’ll read and respond to them in future videos. So, if there’s a specific topic you want me to cover or answer, we have you covered.
I’ll see you next week.
Anthony Fasano, P.E.
Engineering Management Institute
Author of Engineer Your Own Success