SI Spring 14 - 1
Final Exam Review
Ch E 160
DIRECTIONS: The reference sheet plus one extra page of notes may be consulted during the exam. Express all answers in the proper number of significant digits unless directed otherwise.
1. (10%) The air resistance to the motion of a vehicle can be represented by the following equation.
Where: Cd = drag coefficient
Fd = measured drag force, N
r = air density, kg/m3
V = air speed, m/s
A = frontal area of the car, m2
What are the appropriate units for Cd in the equation above? State the units in the simplest terms.
2. A centrifuge and dryer are used to remove water from solid material. A mixture of 38% solids is centrifuged to 65% solids and then dried to 4.0% moisture in the dryer. If 35 kg/h of the final dried material is needed, how much of the 38% solid mixture must be fed to the centrifuge per hour, and how much water is removed per hour?
3. (25%) A company is considering purchasing a machine that costs $20,000 and has a 5 year useful life. At the end of the 5 years, it can be sold for $4,000. If the company could earn revenue of $4,400 per year with this machine, should it be purchased? Assume a 10% annual interest rate.
a) Draw a time line for both the costs and the revenues.
b) What is the net present worth at the beginning of the 5 years of the purchase price minus the present worth of the $4,000 salvage value?
c) What is the equivalent present worth of the revenue at the beginning of the 5 years?
d) Compare the costs to the revenue and answer the question of whether company should purchase the machine. Indicate what values you are using to make this comparison.
4. Using the method of selected points, find the equation of the line shown below. Show your work.
5. (20%) Write a VBA program which will:
a. Read from a data file named, ExamIn.txt. On line one of the file are two integer numbers which are the number of rows, R and the number of columns, C. R and C will never be more than 100 each.
b. Starting on line 2 of the data file are R lines of real numbers with C numbers on each line. Read the numbers that start on line 2 into a 2-dimensional array.
c. Calculate the sum of each row and the sum of the whole array.
d. Determine the percentage of each rows value compared to the whole array:
Sum of Row)¸ (Total Sum) = %. Store these % values in a 1-dimensional array.
e. Output the 2-dimensional array and then the 1-dimensional array to a file named, ExamOut.txt.
Example Output Percentage Array
Two-Dimensional Array 36.68 %
12.3 4.5 11.35 %
3.2 2.0 51.97 %
10.6 13.2
6. Write a complete VBA program that will read in the values of density, velocity, diameter, and viscosity. Calculate the Reynold’s number using the formula given. The program will determine the type of flow of each case and then output on the Excel sheet.
Re= ρ v Dμ where ρ = density, v = velocity, D = diameter, µ = viscosity