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SLAY THE P.E. BLOG

Dissecting the Mechanical PE - Machine Design and Materials Exam: Problem 513

2/6/2017

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Photo via : Les Chatfield
In the NCEES "Sample Questions + Solutions" book, the problems for the afternoon section are numbered 501 through 540. This post is about Problem 513 of the Machine Design and Materials exam.
Description of Problem 513: The problem statement shows a sketch of a cantilever beam. The beam is subject to a distributed load of constant magnitude in a section of its length. You are asked to obtain the internal shear force at a certain location within the beam.

Analysis of Problem 513: This kind of problem is most easily handled with the method of sections: You make a "cut" of the beam at the location of interest - thus "splitting" the beam into two sections. Then apply the equations of equilibrium to one of the two sections. Problem 513 is easier than most solved examples found on this topic in any Strength of  Materials textbook. Here's a similar problem inspired by a solved example we find in Mechanics of Materials by R.C. Hibbeler

Machine Design and Materials Exam Sample Problem #2
The beam is subject to a distributed load as shown:
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Dissecting the Mechanical PE - Machine Design and Materials Exam: Problem 514

2/6/2017

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Photo via : John Donges
In this "dissecting" series of posts we discuss every problem in the NCEES "Sample Questions + Solutions" book. The afternoon section problems in this book are numbered 501 through 540. This post is about problem 514 for the Machine Design and Materials exam.
Description of Problem 514: The problem statement shows a sketch of a simply supported beam. The beam is subject to some external loads. You are asked to obtain the maximum bending moment within the beam.

Analysis of Problem 514: Here you just have to draw the shear force diagram and then the bending moment diagram for the beam. Once you have these diagrams you locate where the maximum bending moment occurs. The most efficient way to do this is with the graphical approach you learned back in the day in engineering school. This approach is reviewed well in the Mechanical Engineering Review Manual by M. Lindeburg, and also in any Strength of Materials textbook (e.g., Mechanics of Materials by R.C. Hibbeler). Here's a similar problem that is a little more challenging than Problem 514, yet it is not harder than anything you did in school:

Mechanical Systems and Materials Depth (PM) Exam Sample Problem #3
Post C-D is fixed to beam A-B as shown. The length d of post C-D is such that the system is in static equilibrium.  
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Dissecting the Mechanical PE - Thermal and Fluids Systems Exam: Problem 506

2/5/2017

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Photo via : Upupa4me
The problems for the afternoon section in the NCEES "Sample Questions + Solutions" book are numbered 501 through 540. This post is about Problem 506 of the Thermal and Fluid Systems sample exam.

Description & Analysis of Problem 506: This is a relatively straightforward U-tube manometer problem. The configuration is very simple and is similar to what is found as a solved example in any Fluid Mechanics or Thermodynamics textbook. The following problem is inspired by a solved example in "Fundamentals of Fluid Mechanics" 6th edition, by Munson, et al.  and is only slightly more complicated than Problem 506.

Thermal-Fluid Systems Exam Sample Problem #1
A closed tank contains compressed air and oil (SG=0.9) as shown in the figure. A U-tube manometer using mercury (SG=13.6 ) is connected to the tank as shown. The column heights are  h1  = 36 in., h2  = 6 in., and h3 = 9 in.
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Dissecting the Mechanical PE - Machine Design and Materials Exam: Problem 504

2/3/2017

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Yielding of ductile member. Photo via : Sean Hagen
In the NCEES "Sample Questions + Solutions" book, the problems for the afternoon section are numbered 501 through 540. Today we are looking at Problem 504 of the Mechanical Systems section.

Description of Problem 504: A figure showing a 3D, statically indeterminate machine element is shown. The element is subject to combined loading. Several geometric dimensions (lengths, radii, height, etc) are provided. You are asked to list the dimensions that are needed to calculate the support reactions.
Analysis of Problem 504: At first, this problem might be somewhat intimidating because it is statically indeterminate and the geometry is three-dimensional. Nevertheless, you do not need to actually find the support reactions - only list the geometric dimensions that would need to be specified in order to find the support reactions. As always, this is actually easier than many strength of materials problems you had to do as undergraduate engineering student. Here is a similar problem we have created to test the same concept:

The post shown in the figure is fixed to to the floor at its base and has a diameter d. External loads P1 and P2 are acting in the x and y directions, respectively. Point A is located on the surface of the post within cross section a – a, which is at a distance h below the line of action of P1 . Distance b is from the axis of the vertical part of the post to the end of the horizontal part of the post.
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Slay the PE Mechanical Systems Depth Sample Problem 001: Strength of Materials. Combined loading. Stress analysis.
Of the following statements, select the one that is true:

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Dissecting the Mechanical PE - HVAC&R Exam: Problem 501

2/3/2017

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Copyright: klotz / 123RF Stock Photo
In this "dissecting" series of posts we will closely look at every problem in the NCEES "Sample Questions + Solutions" book. Today we start with the HVAC and Refrigeration sample questions. In the NCEES "Sample Questions + Solutions" book, the problems for the afternoon section are numbered 501 through 540. We begin our analysis with Problem 501.
Description of Problem 501 : A schematic representation of a refrigeration system is provided. Some data regarding pressure and temperature at certain points are also provided. Thermodynamic properties for the refrigerant in the form of tables and a P-h diagram are provided. You are asked to calculate the coefficient of performance of the system.
Analysis Problem 501 : There is a lot of superfluous/unnecessary information provided in the problem statement that might distract you from the simple fact that what you need to calculate is the COP, which is easy stuff you did in thermo class back in the day. Here is a similar problem we have created (with some distracting/unnecessary data) to test the same concept:
PictureSlay the PE HVAC&R Depth Sample Problem 001: Refrigeration. Vapor compression cycle. Coefficient of Performance
HVAC&R Afternoon Section Problem #1: A refrigeration system for comfort air conditioning in a cruise ship operating with ammonia is schematically shown. The condenser is cooled with 450 gpm of seawater. A network of remotely located fan coil units (FCUs) uses chilled water-glycol provided by this system. You may neglect any pressure loss within the ammonia system.






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Dissecting the Mechanical PE Exam...

2/2/2017

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In these series of posts, we will carefully look at all the problems in the NCEES “Sample Questions + Solutions” books.  Without disclosing the actual problem, we will analyze each one and propose an alternative problem similar in scope and difficulty either of our own design, or from the available literature. This analysis consistently reveals that the problems used in the afternoon portions of the Mechanical PE exam are no more difficult than anything you ever did as an engineering student. The feedback we receive from recent test takers is that the material and level of difficulty displayed in the NCEES "Sample Questions + Solutions" book is still a very good representation of what is in the actual test. Our aim is to shatter the myth of the tremendous difficulty that many people associate with the PE Exam. As you'll see, most of these problems are rather easy if you have prepared well.
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