Questions and Answers of Exploring Engineering Introduction

In 1985 a judge found the structural engineers for the Hyatt Regency Hotel guilty of gross negligence in the July 17, 1981 collapse of two suspended walkways in the hotel lobby that killed 114 and
An electric cart can accelerate from 0 to 60. mph in 15. sec. The Olympic champion sprinter Usain Bolt can run 100.0 m in 9.69 s. Who would win a 100.0 m race between this cart and the world champion
Suppose the gear set is to be used with a motor rotating at a constant speed of 1000. RPM. What are the lowest and highest output speeds that can be developed with the given three gears A, B, and
Now you own a large corporation and a recent economic downturn requires you to eliminate all dividends to your company stockholders. This is a highly confidential decision because it will negatively
As a junior engineer in a small company you are involved in designing a production line for a new product. The company CEO believes that this new product will make a great deal of money and wants to
What is the ROI for the process improvement in Example 16.7 if the factory operates 300 days per year? Would you invest in this company?Example 16.7An engineer proposes an improvement to an existing
Calculate the annual return on investment (ROI) in for the process improvement in Example 16.5 if the factory operates 300 days per year, but sells only 500 widgets per day.
An automobile manufacturer would like to add a new feature to their standard production model. The new feature will cost the manufacturer $8.67 per car to produce, and they expect to sell 100,000
You are a manufacturing engineer and discover that you can purchase a machine that will replace a labor-intensive manual operation in your manufacturing line. The machine costs $1.5 million, but the
In Example 16.7, it turns out that the new process does not save one cent per unit. It only saves 0.3 cents per unit. What is the new BEP, and was it worth the expense to make this
Another long horizon industry is the commercial aircraft industry. A Boeing 747-8 Freighter costs $300 million. A commercial air freight company purchases this plane and keeps it in the air 12 hours
In Example 16.6 the owners of the nuclear power plant decide to use substandard materials to reduce the cost of building and testing the power plant from $8.02 billion to $7.35 billion. If everything
Suppose the new product in Example 16.5 has a profit of $5.00 per widget, but the sales projection is of off by 50 percent and the company is able to sell only 500 per day. What is the new break even
The owners of the nuclear power plant in Example 16.6 want a break even point of five years. To do this, they decide to raise the price of the electricity they sell. For how much do they need to sell
Use the NPER Excel function to determine how long it will take to increase an investment of $3,500 to $4,200 if you earn 3.5 percent interest?
You are a manufacturing engineer and have been asked to project the costs required to produce a new line of products for your company. After contacting the appropriate equipment manufacturers and
Suppose the profit on each widget sold in Example 16.5 was $10.00 instead of $1.00. What would the BEP be if everything else remained the same?Example 16.5Assume the cost of producing a new product
Compare the answer to Exercise 10 with the Rule of Seventy described in Exercise 13.Exercise 13.How long will it take to double your money at an interest rate that is << 100% starting with the
How long will it take to double your money at an interest rate that is << 100% starting with the expression F = P(1 + r)N? ln(1 + r) ≈ r if r << 1 and log (x)N = N log (x)
Use the NPER Excel function to determine how long it will take to triple your $500,000 investment if you earn 11.3 percent interest?
Use the NPER Excel function to determine how long it will take to double your $500,000 investment if you earn 7.5 percent interest?
Repeat Example 16.3 using the Excel spreadsheet FV function to determine the cost of borrowing $3,000 on a credit card for 1 years at 28 percent compounded monthly.
Use the Excel spreadsheet FV function to determine the cost of borrowing $100,000 for 10 years at 5 percent for 87,600 hourly payment periods.
Use the Excel spreadsheet FV function to determine the cost of borrowing $100 billion for 10 years at 8 percent compounded quarterly.
It turns out that the testing phase in Example 16.2 takes six years instead of four years, and the entire project takes 14 years. What will the finance charges be if everything else remains the
What will be the testing phase finance charges in Example 16.2 if the nuclear power plant cost $10 billion and everything else stays the same?
You are a big financial success and you want to purchase the Remlab Company for $35 billion. You have $5 billion in cash, but need to borrow the remaining $30 billion from your friendly banker. You
You need to borrow $12,000 to pay your tuition plus room and board. One bank offers to loan you the money for 10 years at 5.0 percent interest compounded annually. Another bank offers you the loan at
Rework Example 16.1 for a $15,000 loan at a 10% annual interest.Example 16.1You wish to borrow $100,000 for 10 years at 5.0 percent annual interest. What is the difference in the cost of the loan if
Find the cost of borrowing $100,000 in Example 16.1 if the interest is compounded hourly.Example 16.1You wish to borrow $100,000 for 10 years at 5.0 percent annual interest. What is the difference in
As a young engineer, you have been told not to trust the machinists who work for you. They will make up excuses for bad parts that aren’t true because they are lazy or incompetent. One day a
You are a new quality control engineer at a company that manufactures bottled drinking water. All the bottles and the filling water are checked hourly to make sure that there are no contaminants.
You perform 100 tests on one of two prototypes of the X15-24 line of products and a colleague performs another 100 tests on the other prototype.Graphing of the tests is similar with your data as
Quality control is more personal when the products are hand grenades and it’s your turn to learn how to throw one. You understand that once you pull the pin, if you hold on too long you might be
Three hundred widgets are manufactured with the following normal error distribution statistics: mean = 123 units, standard deviation is(a) 23 units,(b) 32.5 units, (c) 41 units. How many will
The jig in Exercise 25 is now OK, except we are getting too many undersized rods passing specifications. The manufacturing section of your company wants to eliminate all rods 0.2 mm or more that are
We wish to fit steel rods (µ = 21.2 mm, σ = 0.20 mm) into the following jig in order to make sure we can meet specifications. The process requires that 97.5% of all rods are to be within
Students often are confused by the difference between a normal distribution curve, as in Exercise 22, and a random distribution. Excel has a variable rand() that will generate random numbers between
The equation for a normal error curve isor in spreadsheet script:Plot a normal distribution curve for the set of 100 numbers from 0 to 99. (x-) exp
In Example 15.5, we did not take into account recycling or disposal costs or benefits. Do you think his conclusions would change if these were included?Example 15.5The energy needed to manufacture a
In the face-milling operation shown below the cutter is 1.5 inches in diameter and the cast iron workpiece is 7.0 inches long and 3.75 inches wide. The cutter has 8 teeth and rotates at 350 RPM. The
A part 275. mm long and 75. mm wide is to be milled with a 10-toothed cutter 75. mm in diameter using a feed of 0.10 mm/tooth at a cutting speed of 40. x 103 mm/min. The depth of cut is 5.0 mm.
A milling operation is carried out on a 10. inch long, 3.0 inch wide slab of aluminum alloy. The cutter feed is 0.01 in/tooth, and the depth of cut is 0.125 inches. The cutter is wider than the slab
A flat piece of cast iron 100. mm wide and 150. mm long is to be milled with a feed rate of 200. mm/ minute with a depth of cut of 1.0 mm. The milling cutter rotates at 100. RPM, and is wider than
Repeat the calculations in Example 15.4 for stainless steel instead of cast iron. Use the same material dimensions and operating conditions, and compare the machining times for the two materials.
You need to drill a 20. mm hole in a piece of stainless steel. The drill feed is 0.10 mm/revolution and its rotational speed is 400. RPM. Determine:a. The material removal rateb. The power requiredc.
A drill press with a 0.375 inch diameter drill bit is running at 300. RPM with a feed of 0.010 in/rev. What is the material removal rate?
Suppose the material used in Example 15.3 was an aluminum alloy and the drill rotational speed was 500. RPM. Recalculate the material removal rate, the power required, and the torque on the drill.
A 2.0 inch diameter carbon steel shaft is to be turned on a lathe at 500. RPM with a 0.20 inch depth of cut and a feed of 0.030 in/rev. What is the minimum horsepower and torque that the lathe must
A lathe is powered by a 5.0 HP electric motor and is running at 500. RPM. It is turning a 1.0 inch cast iron shaft with a depth of cut of 0.035 in. What is the maximum feed rate that can be used
Determine the machining time required to turn a 0.20 m long shaft rotating at 300. RPM at a tool feed of 0.20 mm/rev.
Determine the machining power and cutting torque required to machine a magnesium shaft on a lathe if the material removal rate (MRR) is 0.1 in3/min and N = 900. RPM.
Repeat the calculations in Example 15.2 for a magnesium alloy being machined at 700. RPM.
A shaft 150. mm long with an initial diameter of 15. mm is to be turned to a diameter of 13.0 mm in a lathe. The shaft rotated at 750. RPM in the lathe and the cutting tool feed rate is 100.
Using Taylor’s equation in Exercise 4, show that tool wear and cutting speed are related by T2 = T1(V1/V2)1/n.Exercise 4VTn = C
For a particularmachining operation n = 0.6 and C = 350 mm/min0.4 in the Taylor equation given in Exercise 4. What is the percentage increase in tool life when the cutting speed V is reduced by (a)
Tool wear is a major consideration in machining operations. The following relation was developed by F. W. Taylor for the machining of steels:VTn = Cwhere V is the cutting speed; T is the tool life;
For a particular casting process the constant K in Chvorinov’s equation in Exercise 2 is 3.00 s/mm2 for a cylindrical casting 150.mmhigh and 100.mmin diameter. Determine the solidification time for
A casting process involves pouring molten metal into a mold, letting the metal cool and solidify, and removing the part from the mold. The solidification time is a function of the casting volume and
Discuss the building materials used by the three little pigs (straw, sticks, and bricks). Why were they chosen? Why did they fail? What was the environmental impact?
During World War II, Nazi Germany conducted human medical experimentation on large numbers of people held in its concentration camps. Because many German aircraft were shot down over the North Sea,
You are now a supervisor in the bioengineering department of a major motorcycle helmet manufacturer. Your engineers are testing motorcycle helmets manufactured by a variety of your competitors.
As a bioengineer at the Crash Safety Test Facility of a major automobile company, you are asked to provide more data for the Gadd Severity Index (Figure 14.6). Your boss suggests using live animals,
Which do you think has been more effective in reducing fatalities on American highways, seat belts or air bags? Give an engineering reason for your answer, containing variables, numbers, and units.
A car strikes a wall traveling 30. mph. The driver’s cervical spine (basically the neck) first stretches forward relative to the rest of the body by 0.010 m and then recoils backward by 0.020 m as
A soccer player “heads” a wet 0.50 kg soccer ball moving directly toward him by striking it with his forehead. Assume the player initially moves his head forward to meet the ball at 5.0 m/s and
A designer of football helmets has two options for increasing the safety of helmets but for economic reasons can implement only one. One option is to double the area of contact that will be
Two 100 kg football players wearing regulation helmets collide helmet to helmet while each is moving directly at each other at 10.0 m/s and come to a near instantaneous (<1 millisecond) stop. The
The air bag is designed to inflate very quickly and to subsequently yield if the driver hits it. A collision uniformly stops a car from 30. mph to 0.0 and then triggers the air bag. The driver is not
A 75. kg person jumping from a 1.00 × 103 m cliff will reach a terminal speed of 50. m/s and uses a 1.00 × 102 m bungee cord to slow the descent. The bungee cord exerts a force F proportional to
The parachutist in the previous two exercises hits the ground (still wearing the parachute!) and is stopped in a distance of 0.10 m. If this final deceleration is constant, calculate the Gadd
In the previous problem, the force exerted by the parachute is spread by a harness in contact with 0.50 m2 of the parachutist, and the parachutist has a mass of 75. kg. What is the force per unit
Consider a parachute as a safety device. When the parachute opens, the previously freely falling person typically has reached a speed of about 50. m/s. The parachute slows to a terminal speed of
1. Provide a graph of v-t of the collision of the skull and the windshield, and then graph the force experienced by the skull as a function of time.A car is traveling 30. mph and hits a wall. The car
A rear-facing child safety seat holds a child of mass 25. kg rigidly within the rigid interior of a car. The area of contact between the seat and the child is 0.10 m2. The car undergoes a 30. mph
A rear-facing child safety seat holds a child of mass 12. kg rigidly within the interior of a car. The area of contact between the seat and the child is 0.10 m2. The car undergoes a 30. mph
A tall person sits down on a sofa to watch TV. Assume that the center of gravity of the person falls 1.0 m with constant gravitational acceleration in the course of sitting down. The sofa compresses
Prepare v–t and F–t graphs of Stapp’s trip, and compute the g forces he experienced in the course of acceleration and deceleration.In the 1950s when Air Force Colonel John Paul Stapp
Using the force vs. time graph (Figure 14.6) for human resistance to g forces, predict whether Stapp suffered serious injury in the course of his record-breaking trip.In the 1950s when Air Force
If the compressive strength of bone is 3.0 x 106 N/m2, will the collision in the previous exercise break the skull?A car is traveling 30. mph and hits a wall. The car has a crumple zone of zero, and
You are an engineer on a team designing a bridge for a state government. Your team submits what you believe to be the best design by all criteria, at a cost that is within the limits originally set.
You are an engineer with the responsibility for choosing the route for a new highway. You have narrowed the choice to two sites that meet all safety standards and economic criteria (call them Route A
Consider only two of the gears in the gear set, the 12–36 and 12–42 tooth gears. For any given input speed, how many different output speeds are possible? Illustrate by categorizing the number of
A motor drives a shaft at 1000. RPM with a torque of 35 newton meters. A gear on that shaft has 42 teeth. That gear drives a second gear with 12 teeth. That second gear is connected to an output
Suppose gear A was driven by a motor at 1800. RPM. Suggest an arrangement of gears from the given gear set A, B, and C to achieve an output speed of 18,900 RPM.Concern a gear set consisting of up to
If the drive gear in Exercise 21 is rotating clockwise, what is the direction of rotation of the driven gear?Concern a gear set consisting of up to the three gears as shown here. In each case the
Suppose an 1800.0 RPM motor is connected directly to gear A. The 12 tooth portion of gear A drives the 42-tooth portion of gear B. What is the rotational speed in RPM of the shaft of gear B?Concern a
Imagine a smart car of the future with radar and computer control capabilities that make it safe to operate on today’s highways with twice the speed and half the spacing of today’s human-driven
If you want to achieve a flow of 2,600 cars per hour in each direction on a highway, and the two-second rule applies, how many lanes must the highway have in each direction?
This chapter has shown that for the two-second rule the number of cars per hour completing a trip is independent of speed. Consider now a slightly more realistic follow rule: mph =
You are a TV reporter who rides in a helicopter to advise commuters about their travel time from their bedroom community to a city 20. miles away. You notice from your helicopter there are 160 cars
You wish to cover a two-mile trip at an average of 30.0 mph. Unfortunately, because of traffic, you cover the first mile at just 15.0 mph. How fast must you cover the second mile to achieve your
Suppose that a human body can withstand an acceleration of 5.0 gee, where 1 g is 9.8 m/s2. How long would the cannon have to be in the previous exercise to keep the acceleration of the humans within
An early proposal for space travel involved putting astronauts into a large artillery shell and shooting the shell from a large cannon. Assume that the length of the cannon is 30. m and that the
Suppose the deceleration of a car on a level off-ramp is -3.0 m/s2. How long would the off-ramp have to be to allow a car to decelerate from 60. mph to 15. mph?
Assume that the purpose of an on-ramp is to allow cars to accelerate from 15. mph to 60. mph. An offramp will allow cars to decelerate from 60. mph to 15. mph. Should an off-ramp be longer than,
The distance d in meters from which a person can see a stop sign is given by the formula D = d/30. (where D is the diameter of the stop sign in meters). Assume it takes a person one second to step on
Why are red lights on the top of traffic lights and green lights on the bottom?
You are a driver responding to the traffic light in the previous exercise. If it was correctly designed according to that problem, at what distance from the light should you be prepared to make your
You are an engineer designing a traffic light. Assume a person can see a traffic light change color from red to yellow, and it takes one second to respond to a change in color. Suppose the speed

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