C OMMUNICATION
Step 4: Verifying the Results
The final step of any engineering analysis should be the verification of results. Various sources of error can contribute to wrong results. Misunderstanding a given problem, making incorrect assumptions to simplify the problem, applying a physical law that does not truly fit the given prob- lem, and incorporating inappropriate physical properties are common sources of error. Before you present your solution or the results to your instructor or, later in your career, to your manager, you need to learn to think about the calculated results. You need to ask yourself the following question:
Do the results make sense? A good engineer must always find ways to check results. Ask yourself this additional question: What if I change one of the given parameters. How would that change the result? Then consider if the outcome seems reasonable. If you formulate the problem such that the final result is left in parametric (symbolic) form, then you can experiment by substituting dif- ferent values for various parameters and look at the final result. In some engineering work, actual physical experiments must be carried out to verify one’s findings. Starting today, get into the habit 4.2 Basic Steps Involved in the Solution of Engineering Problems
93
Course number
Problem number
The purpose of a diagram is to show the given
information graphically. By drawing a diagram, you are
forced to focus and think about what is given for a problem. On a diagram you want to show useful information such as dimensions, or represent the interaction of whatever it is that you are investigating with its surroundings. Below or along side of the diagram you may list other information that you cannot easily show on the diagram.
List all assumptions. Show completely all steps necessary, in an organized, orderly way, for the solution.
In this block you want to itemize what information you are searching for.
Number of this sheet Total number of sheets in the assignment
Answer SKETCH
Date due
Assignment number
Last name, first name
1 2
1.
2.
3.
GIVENFINDSOLUTION
SHOW CALCULATIONS ON RIGHT-HAND SIDE.
SHOW ANY DIAGRAMS THAT MAY COMPLEMENT THE SOLUTION ON THE LEFT-HAND SIDE.
Double underline answers.
Do not forget about units.
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Figure 4.1 An example of engineering problem presentation.of asking yourself if your solution to a problem makes sense. Asking your instructor if you have come up with the right answer or checking the back of your textbook to match answers are not good approaches in the long run. You need to develop the means to check your results by asking your- self the appropriate questions. Remember, once you start working for hire, there are no answer books. You will not want to run to your boss to ask if you did the problem right!
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4.3 Homework Presentation
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4.3 Homework Presentation
Engineering paper is specially formatted for use by engineers and engineering students. The paper has three cells on the top that may be used to convey such information as course number, assignment due date, and your name. A given problem may be divided into a “Given” section, a “Find” section, and a “Solution” section. It is a good practice to draw horizontal lines to sep- arate the known information (Given section) from the information that is to be found (Find section) and the analysis (Solution section), as shown in Figure 4.1. Do not write anything on the back of the paper. The grid lines on the back provide scale and an outline for freehand sketches, tables, or plotting data by hand. The grid lines, which can be seen from the front of the paper, are there to assist you in drawing things or presenting tables and graphical informa- tion on the front of the page neatly. These grid lines also allow you to present a freehand engi- neering drawing with its dimensions. Your engineering assignments will usually consist of many problems, thus you will present your work on many sheets, which should be stapled together.
Professors do not generally like loose papers, and some may even deduct points from your assign- ment’s total score if the assignment sheets are not stapled together. The steps for presenting an engineering problem are demonstrated in Example 4.1. If you are presenting solutions to simple problems and you think you can show the complete solution to more than one problem on one page, then separate the two problems by a relatively thick line or a double line, whichever is more convenient for you.
E xa m p l e 4.1 Determine the mass of compressed air in a scuba diving tank, given the following informa-
tion. The internal volume of the tank is 10 L and the absolute air pressure inside the tank is 20.8 MPa. The temperature of the air inside the tank is 20⬚C. Use the ideal gas law to analyze this problem. The ideal gas law is given by
PV⫽mRT where
P ⫽absolute pressure of the gas, Pa V⫽volume of the gas, m3
m⫽mass, kg R⫽gas constant,
T⫽absolute temperature, Kelvin, K
The gas constantRfor air is 287 J/kg
⭈
K. At this time, do not worry about understanding the ideal gas law. This law will be explained to you in detail in Chapter 11. The purpose of this example is to demonstrate how a solution to an engineering problem is presented. Make sure you understand and follow the steps shown in Figure 4.2.J kg
#
K96
Chapter 4 Engineering CommunicationME 101
Mass of air inside the tank, m = ? Problem 3.1
A tank of compressed air P = 20.8 MPa
V = 10 liters = 0.01 m3 R = 287
T = 20°C = 293 K
Assuming ideal gas behavior
PV = m RT Eq(1)
where
P = 20.8 MPa = 20.8 X 106 V = 10 liters = 0.01 m3 R = 287
T = 273 + 20 = 293 K Substituting into Eq (1)
( 20.8 X 106 )(0.01 m3) = m( 287 )(293 K) and realizing that 1 J = 1 N · m,
m
12 Sept. 2001 ASGT. No. 1 Happy, Joe 1 1
GIVENFINDSOLUTION
Any assisting diagrams
Always double-underline answers and state units
Index answer Calculations on the right
m = 2.473 Kg air
N m2
N m2
J Kg · K
J Kg · K J
Kg · K
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Figure 4.2 An example of engineering homework presentation for Example 4.1.62080_04_ch04_p091-108.qxd 5/25/10 9:46 PM Page 96
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4.4 Progress Report, Executive Summary, and Short Memos Progress Report
Progress reports are means of communicating to others in an organization or to the sponsors of a project how much progress has been made and which of the main objectives of the project have been achieved to date. Based on the total time period required for a project, progress reports may be written for a period of a week, a month, several months, or a year. The format of the progress report may be dictated by a manager in an organization or by the project’s sponsors.