IOE 333: Homework #2 100 points Due: Friday, February 26, 2010, 11:30 am on CTools After the due time, CTools will not accept any homework. Please type your answers in this file below each question. Save your file name using your unique name in the following format: uniquename_IOE333HW2 And upload your file to CTools -> Assignment Section 1 (55 points) Briefly describe any one PHYSICAL task or activity of your interest, and propose YOUR OWN technological innovation and/or task procedure change to help improve physical performance or reduce physical stress or workload. Use physical ergonomics concepts/methods to explain (or ?promote/sell?) your proposal (use your imagination; show your innovative spirit?this is most important for this problem). (8 pts) Carrying a heavy backpack everywhere can really be damaging for the lower back especially for college students. My technological innovation is to have a backpack that is able to distribute the weight in such a way where the user doesn?t feel the weight pretty much at all. This way the L5/S1 disk won?t be experiencing such a large compression force for a long period of time. Which part of which story in the ?cultural ergonomics? article best illustrates a PHYSICAL ergonomics problem in the global CULTURAL context? How do you propose to deal with it (it is fine if you cannot settle on one solution, as long as you briefly discuss the pros and cons of two or more possible approaches). (8 pts) The part of the article discussing the hotel supplying oxygen illustrates how different locations have different problems. For example, the hotel was so high above sea level that it didn?t have a good supply of oxygen. The ergonomics design for this location would be different from a location is close to sea level. In order to deal with this problem, industrial and operational engineers need to understand the location and the culture of that location in order to make things effective. Briefly explain why aerobic metabolism enables a person to work almost indefinitely while a person can only work for a short period of time when utilizing anaerobic metabolism. (5 pts) Aerobic metabolism needs oxygen to function. Since oxygen rarely runs out then so a person is able to work almost indefinitely Anaerobic metabolism functions without oxygen. People can go without oxygen for only a small amount of time so a person utilizing anaerobic metabolism can only work for a short period of time. What are the two types of muscle strength? Describe the method for measuring each type of muscle strength. (5 pts) Static strength is the maximal voluntary isometric muscle exertion level. Static strength is measured when a group of static exertions is performed. Each last about 4 to 6 sec, with 30 to 120 sec rests provided between exertions. Dynamic strength can be measured by using designed isokinetic equipment to ensure fixed-speed body motion by providing a variable resistance to the motion. List 5 potential causes of low-back pain. For each of your listing, use one or two sentences to briefly describe why it may be a cause. (5 pts) Age: People?s L5/S1 get more and more damaged with age because the bones get weaker Posture: Chairs: If someone sits at a badly design chair for longs periods of time then their back is not getting any support and a lot of force is getting directed to a small area. Lifting heavy items: If someone lifts really heavy items very frequently then their L5/S1 constantly gets a lot of force directed to it making it weaker. Suppose there is a large group of people having normal distributed height with mean 175 cm and standard deviation 10 cm. Given a person from this group and that only 10 percent of people in the group are higher than this person, what will be the height of this person? (4 pts) X = M + F*s M = 175cm F = 1.282 (from table 10.1) S = 10cm X = 175 + 1.282*10 X = 187.82 cm List 5 of the general principles for work-space design? Give a specific example for each principle. (5 pts) Clearance requirements of the largest users A door being tall enough for the average tallest person Reach requirements of the smallest users The smallest reach for a person while driving in a car Special requirements of maintenance people A maintenance person might be able to fit into a space without their uniform but with it on they should be able to still fit. Adjustability requirements Office chairs should be able to adjust for all employees Component arrangement A bus driver should have its important / most used controls closer to him for easy access. What is the ?normal line of sight?? Does placing information or displays within the normal line of sight insure that it will be processed by the person? Why or why not? (5 pts) The normal line of sight is the preferred direction of gaze when the eyes are at condition. (about 10° to 15° below the horizontal plane) No, presenting material within 15° around the normal line of sight is not sufficient to ensure that it will be processed. The visual angle, the contrast of the material, and the viewing distance must also be adequate for resolving whatever information is presented there. Answer the following two questions using the Table 10.2 and the Figure 10.4 in your textbook. What body dimensions would you need to design the following exercise bicycle? (5 pts) Popliteal Height Hp Breadth Foot length Foot breadth Forward function reach What should be the range of adjustment for the seat? (5 pts) The range should be 15.1 inches to 18.4 inches. The range should be from the lowest popliteal height (5th percentile) to the highest popliteal height (95 percentile) ALWAYS SHOW ALL COMPUTATIONS. Final answers alone are not acceptable when computation is required. Section 2 (15 points) For workers from the general civilian population, how much seated rest (in minutes/hour of work) should be allotted for a floor-level lifting task that is only performed 1 to 2 hours per work day and requires an oxygen consumption rate of 1.5 liters/minute? PWC= 3.7 kcal/min Ejob= 1.5 L/ min= 7.35 kcal/min= 441 kcal/hr Erest = 90 kcal/hr QUOTE hr/min = 37.44 min/hr An individual worker has a heart rate of 103 bpm (beats per minute) during the period of 30 seconds to one minute and 95 bpm during the period of 2.5 to 3 minutes immediately after completing a strenuous task. Is this task too demanding (or, fatiguing) for the worker? Justify your answer. This task is too fatiguing for the worker. Using individual fatigue monitoring the following rule occurred making the task too demanding. HR30-60-HR150-180 < 10 beats/min and HR150-180 > 90 beats/min Section 3 (15 pts) When Monica does laundry, she lifts the laundry basket off the floor with the posture shown in the drawing below. Gravity forces are 150N for the Laundry basket, 350N for the torso, and 36N for each arm. Assume the mass center of torso is 25% torso length away from the center of the two shoulder joints, and the mass center of an arm is the middle point of the arm (from shoulder joints to fist). Assume that Monica is a 50 percentile female, and her arms are straight in this task. Use anthropometric data to determine all dimensions needed to solve this biomechanical problem. Forward Functional Reach: 24.6in=62.48cm Mid-shoulder Height: 22.8in=57.91cm What is the back muscle force required to maintain this posture? Fmuscle * 5 = Wload*h + Wtorso*b + 2 * Warms*x x =distance from L5/S1 to middle of arms h = distance from L5/S1 to middle of load b = distance from L5/S1 to torso b = .75*57.91*sin(60) = 37.61cm h = 57.91*sin(60) +62.48*cos(45) = 94.33cm x = 57.91*sin(60) +0.5*62.48*cos(45) = 72.24cm Wload= 150N Wtorso= 350N Warm=36N Fmuscle = (150*94.3+350*37.61+2(36*72.24))/5 Fmuscle = 6501.96N Section 4 (15 pts) Joe needs to move a container onto a storage shelf. The container has 10 movable objects in it, each weighing 2 kg, and the container itself weighs 2 kg and has good handles. To place the container in the correct place, he has to twist his torso 45 degrees. The diagram below illustrates this activity. The handles of the container being lifted is located 40 cm horizontally from the center of his ankles. The handles and center of mass of the container are located 10 cm off the bottom of the container. The shelf?s top surface is 80 cm above the floor. 1. If Joe wants to move everything onto the shelf together in one lift, is it OK according to the NIOSH lifting guide? You can assume that Joe does not need to lift other things that day (Show all your calculations). RWL = LC*HM*VM*DM*AM*FM*CM LC = 23.2 kg HM = 25/40 = .625 VM = (1-.003* |10-75|) = .805 DM = (.82 + 4.5/80) = .876 AM = 1-.0032 *45 = .856 FM = .94 CM =1 RWL = 23.2*.625*.85*.876*.856*.94*1 RWL = 8.22 kg According to the NIOSH lifting guide, lifting 10, 2kg boxes at one is over the limit 2. What method would you recommend for this lift to make sure it is safe? Justify your answer with related calculations. I recommend the squat lift ? straddle stance because it has the lowest peak L5/S1 compression force at 400 N so I assume that it will still have the lowest peak at 200N (20kg). PAGE PAGE 1
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