## Why Free Videos?

I have taught every mechanical engineering undergraduate course: statics, dynamics, solids, fluids, thermal I and II, heat transfer. All of the basic courses that are part of the DTC Mechanical PE Exam Review. I’ve taught them many, many times, and I just love to see the light bulb go on when a student finally understands how to solve a problem. Because it really shouldn’t be mystery. It is hard and it takes hard work, but I have always enjoyed finding a way to help my students understand mechanical concepts and apply them.

That’s why I’m offering free videos, to help people make that leap of understanding. I created these videos to help folks taking the Mechanical PE Exam as I come across topics in the MERM and NCEES Practice Exam that needed greater clarification beyond my DTC PE Exam Review. But from the response we have received, they have turned out to be valuable to anyone studying these concepts. The video on Distributed Loads has been watched over 40,000 times and the other top videos on Slider-Crank, Vehicle Dynamics, Zero-force Members and other topics have been watched many thousands of times.

My goal is to keep adding new free videos as I come across topics that need them. The more I’ve worked with mechanical engineers and helping them prepare for the PE Exam, the more I have realized what a difference getting your PE can make in a person’s life. I get so excited when our participants pass the exam. That really is what I enjoy most about all this, helping to change people’s lives.

#### – Dr. Tom

### NCEES ME PE Sample Exams – Instructional Companion Videos

The goal of these videos is to address selected problems on the NCEES Sample Exams that have solutions that caused confusion with participants in my Mechanical Engineering PE Exam Review Courses.

DTC recommends that anyone taking the PE Exam purchase the NCEES Practice Exam for the exam they are taking. It is an essential exam review resource. https://account.ncees.org/exam-prep/

NCEES TFS Problem 112 in the NCEES Mechanical Practice Exam for Machine Design & Materials has been one of the more troublesome NCEES MDM Practice Exam problems for our participants. The solution begins with an equation that results in questions like “where did that come from?” When I first looked at the solution I had the same question. What is lacking is a statement up front that the change in length of the bar must equal the change in length of the spring. The bar gets longer because of the increase in temperature, but it simultaneously gets shorter because of the increase in the force in the spring. Once you do that, you get the equation they started with. This is actually a great problem, and I hope my explanation helps you to understand all its fundamental concepts.

– Dr. Tom

DTC recommends that anyone taking the PE Exam purchase the NCEES Practice Exam for the exam they are taking. It is an essential exam review resource. https://account.ncees.org/exam-prep/

NCEES Problem 510 in the Machine Design and Materials Practice Exam (2106) is a classic 2D equilibrium problem involving a mechanical device to hold up a weight by friction based forces. However, the solution presented by the NCEES is incorrect. In the application of one of the equilibrium equations to the free-body diagram of one of the two major pieces, two terms are missing. In the NCEES solution these two terms supposedly cancel when in fact they do not. One the shortfalls of the NCEES solution is that the free-body diagram of the piece in question is not provided. In this Instructional Companion, the Dr. Tom Method provides the necessary free-body diagrams and associated equilibrium equations.

Dr. Tom

DTC recommends that anyone taking the PE Exam purchase the NCEES Practice Exam for the exam they are taking. It is an essential exam review resource. https://account.ncees.org/exam-prep/

Problem 521 in the NCEES Mechanical Practice Exam for Machine Design & Materials has a very straightforward solution, however the origin of the equation used was not clear to participants in our review or myself. Consequently, there was great discussion in our DTC Participant Forum as to where it came from until one of the participants realized how it could be obtained. This Instructional Companion provides the details of the approach suggested by that participant.

– Dr. Tom

NCEES MDM Problem 538 in the NCEES Mechanical Practice Exam for Machine Design & Materialsfalls under the topic “Static Design” and has a fairly straightforward solution, except that it’s not obvious where the equation came from that it uses for calculating the distortion energy stress. We have had a lot of questions in the participant forum for our MDM review course about its origin. This video shows where that equation comes from, and in the process provides a powerful general equation for other similar type problems. The video also fills in a few details left out of the NCEES solution.

NCEES TFS Problem 114 is a classic mixing chamber problem, however the first equation given in the NCEES solution makes it look like you get the answer by “averaging” the enthalpies, but could have used any of the other intensive properties like specific volume, specific internal energy, or specific entropy. But you cannot. What is missing in the NCEES solution is the application of both Conservation of Mass and Conservation of Energy, meaning the 1st Law for Open Systems. In this video I show those missing steps, an how the magnitudes of the mass flow rates given and that only enthalpy can be used determines the answer. I also provide you with a general equation that would apply to similar problems with any given mass flow rates. This is a perfect example of the application of the Dr. Tom Method and its effectiveness in solving classes of problems.

Dr. Tom

Problem 139 in the NCEES Mechanical Practice Exam for Thermal & Fluids Systems is a classic problem that involves finding the coefficient of performance (COP) of a heat pump. You are given a table of the pressure, temperature, and most importantly the enthalpy at all four points in the cycle. (Note the enthalpy at point 4 equals that at point 3.) The problem and NCEES solution are very straightforward and you should have no trouble following the steps.

However, there have been problems where you are told that the evaporator has so many “degrees of superheat,” or the condenser has so many “degrees of subcooling.” What do these terms mean? The purpose of this presentation is to explain how these fit into the standard heat pump cycle. By the way, these terms could also show up for an air conditioner or refrigerator, but they mean the same for the respective elements of the cycle.

– Dr. Tom

This is an Instructional Companion to Problem 507 in the New 2016 NCEES Thermal & Fluids Systems Practice Exam.

This is an Instructional Companion to Problem 530 in the New 2016 NCEES Thermal & Fluids Systems Practice Exam. It was Problem 516 in the old NCEES Practice Exam.

This is an Instructional Companion to Problem 530 in the New 2016 NCEES Thermal & Fluids Systems Practice Exam. It was Problem 516 in the old NCEES Practice Exam. It is a Bonus presentation in that it shows how determine the efficiency between states (1) and (3).

Problem 537 in the NCEES Mechanical Practice Exam for Thermal & Fluids Systems is straightforward, however it has a major intimidation factor when you first come to it in the Practice Exam and would if a similar problem was on the actual exam. Lots of information taking up an entire page, and a very complicated schematic of the cogeneration plant. In this presentation I go through the strategy and steps to approach this problem with calm and confidence. I hope it adds to your ability to handle these kinds of problems successfully.

– Dr. Tom

Problem 525 on the Old NCEES Practice Exam involving a gas turbine. The new Practice Exam has some similar problems so this video is still applicable and will help you understand the solutions for the new problems.

Problem 525 on the Old NCEES Practice Exam involving a gas turbine. The new Practice Exam has some similar problems so this Bonus video is still applicable and will help you understand the solutions for the new problems.

### MERM Instructional Companion Videos

The following videos address some of the shortfalls of the MERM, particularly in the topics of Statics and Dynamics. These videos have become very popular with engineers and engineering students around the country. They also supplement the lessons contained in Dr. Tom’s ME PE Exam Review Courses, and provide a solid foundation in some topics and enhance particular areas in other topics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Pulleys in the chapter Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Two-force Members in the chapter Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Two-Dimensional Mechanisms, which I call 2D Frames, in the chapter Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Zero-force Members in the chapter Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Distributed Loads in the chapter Determinate Statics.

This is an Instructional Companion to Example 45.1 in the MERM relative to finding the Simplest Resultant of a Distributed Loading on a beam.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on 2D Reactions in the chapter Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the sections on Determinacy and Types of Beams in the chapter Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the sections on Finding Reactions in Two Dimensions in the chapter Determinate Statics. The beam used in other Instructional Companion is the beam presented.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the sections on Couples in the chapter on Determinate Statics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, presenting the argument for using “slug” vs “lbm” in Mechanics and Fluids.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Flat Friction in the chapter Kinetics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Flat Friction in the chapter Kinetics.

This is an Instruction Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Power in the chapter Energy, Work, and Power.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Rigid-body and Relative Motion in the chapter Kinematics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on Slider Rods in the chapter Kinematics. Example worked is from the NCEES Sample Exam, Mechanical Systems PM.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the Velocity of Rolling Wheels in the section on Rotation about a Fixed Axis in the chapter Kinematics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the Acceleration of Rolling Wheels, NOT included in the section on Rotation about a Fixed Axis in the chapter Kinematics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the topic Rigid-Body Kinetics in the chapter Kinetics.

This is an instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the sections on Vehicle Dynamics in the chapter Kinetics.

This a continuation of Vehicle Dynamics I where the use of the D’Alembert’s Principle of Dynamics Equilibrium can be extremely confusing to follow, and worse result in wrong answers.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on rotational to translational motion of a pulley and block, acting like a Simple Hoist, in the chapter Kinetics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the section on rotational to translational motion, a pulley and block being a Simple Hoist, in the chapter Kinetics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the dynamics of rolling wheels in the chapter Kinetics.

This is an Instructional Companion to the MERM, the Mechanical Engineering Reference Manual, covering the dynamics of Rolling Wheels in the chapter Kinetics.

This is a postscript to the MERM Instructional Companion – Wheel Dynamics II, where the result obtained on the last page, that the torque (T) was equal to the force (P) times the radius (R), made too many unlikely assumptions.

Presented are some final thoughts on the MERM Instructional Companions: Wheel Dynamics I and II, and T = PR???, specifically on what happens when the Drive Wheel and Push/Pull Wheels are connected by a solid frame.

### Fluid Mechanics Review Videos

These videos review the topics within Fluid Mechanics that are likely to appear on the ME PE Exam. The videos are much like the lessons provided in Dr. Tom’s ME PE Exam Review Courses.

In Fluid Mechanics Review – Part I, I discuss “What the NCEES Specifications don’t tell you!” and what I recommend you do about it.

The Fluid Mechanics Review – Part II covers Fluid Properties and includes a discussion of viscosity for Couette and Poiseuille Flows.

The Fluid Mechanics Review – Part III covers the Continuity Equation and begins with a discussion on the Types of Fluid Flow.