Midterm practice quesions from each group

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Apr 3, 2024

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Group 20 Which of the following statements are TRUE? 1. In the Revised NIOSH Lift Equation, the larger the recommended weight limit (RWL) or the lower the lifting index (LI), the more protective the task is to workers. [TRUE] 2. Observing one cycle and/or 5 minutes of a task is adequate when measuring repetition or exposure of a task [FALSE] 3. When making a design to accommodate the 5th percentile female through the 95th percentile male, you are accommodating for 95% of the population [FALSE] 4. When calculating the Bloswick Shoulder Movement, the load should be divided in half if it is a 2-handed lift. [TRUE] 5. The human factors engineering approach to design is a cycle of creating, evaluating, and understanding. [TRUE] Group 21 Given below is a photo of a bricklayer in the middle of a task of building a wall. Inspect the image and answer the following questions: a) Perform a REBA analysis based on the joint angles/posture visible in the image. If any assumptions are made (even with respect to prior knowledge), please list them. Show all numbers and calculations used to get to your final REBA score. i) Assume that the load of each brick is 5 lb. ii) Assume Wrist Score = +1 and Coupling = +2. iii) Assume Activity Score = +2. b) List 2 musculoskeletal disorders which might occur from repeated occurrences of the task as it is. c) Based on the REBA analysis, which 2 muscle groups would you target the most in improvements? Give 1 reason for each.

Source Correct Answer: a) REBA analysis Neck: 2 Legs: 2 Trunk: 4 Posture Score A = 6 Force/Load Score = 0 Score A = 6 Upper Arm: 3 Lower Arm: 1 Wrist: 1 Posture Score B = 3 Coupling Score = 2 Score B = 5 Table C = 8 Activity Score = 2 Final REBA Score = 10, high risk, investigate and implement change

b) i) Chronic back pain could occur in the form of slipped discs and sciatica due to sustained back flexion accompanied by a relative lack of knee extension in the frontal plane. ii) Myofascial pain syndrome could occur due to a high degree of sustained neck extension with respect to the torso in the frontal plane. iii) Rotator cuff tendonitis, from working with arms elevated more than 60 degrees from the trunk (p. 438 in “Musculoskeletal Disorders” book in module 2) for long periods of time. iv) Bicep tendonitis can be caused due to repeated arm extension with a load in the frontal plane. c) Based on the REBA analysis, the 2 muscle groups which would need the highest priority are: ● Back: Due to the highest endpoint given as per the REBA analysis along with a very steep angle of flexion accompanied with an inappropriate hip hinge movement. ● Neck: Due to repeated neck extension occurring in every cycle of the task as well as a maximum REBA score given. Group 1 Q: Here is an Amazon worker who needs to carry different loads of different weights every day. As a matter of fact, after years and years of work, his back hurts consistently and he wants to know on average how much pressure his back feels each time he moves a

load. Here is a graph of how he works daily and please find out how much back compressive force he experiences every time. Solution: Back Posture (A) = 3 * 160 * sin(30) = 240lb ; Load Moment(B) = 0.5 * 10 * 20 = 100lb ; Direct Compresion(C) = 0.8*(80+ 10) = 72lb; Hence the total back compressive force is A + B + C = 412lb. Q: Given that a person has a body weight of 150 pounds, they're lifting a load of 40 pounds at 67 degree angle, and the horizontal distance is 12" calculate the estimated back compressive force. A: 405 + 240 + 92 = 737 Q: A man weighing 160 lbs is picking up a box from the ground. The box weighs 20 lbs, and the man's back angle is 90 degrees from the vertical. He lifts the box with a horizontal distance of 20 inches. Calculate the total back compressive force. Based off the force, should changes be made to the action? A: BW = 160 lbs, LW = 20 lbs, HB = 20 inches Back = 3 * 160 * 1 = 480 Load = 0.5 * 20 * 20 = 200 Direct = 0.8[(160/2) + 20] = 80 Total Force = 480 + 200 + 80 = 760 lbs Yes, changes should be made to this action because the total estimated compressive force is 760 lbs, which exceeds the comparison value of 700 lbs. However, because this value is decently close to the comparison value, we can also have a more detailed analysis to this problem to see how different hand motions and actions affect the estimated compressive force. Question: Using the below picture of an endoscopic procedure as a reference, please list the relevant physical task demands for the procedure. An endoscopic procedure involves navigating a tube-like device called an endoscope through a patient’s gastrointestinal tract where a camera is attached at the end to gain visual insight.

Here is another picture of the environment in which the procedure is performed for additional context. Answer: Force: ● The doctor must apply a constant force equal to the mass of the endoscope times the acceleration due to gravity throughout the exam in order to hold up the endoscope. ● The doctor’s positioning is causing a force on their lower body as they are standing throughout the exam. Repetition: ● The hand/fine motor movements to do with adjusting and moving the endoscope are continually repeated throughout the procedure.

Contact/Mechanical Stress: ● While there is a gap between the part of the device the doctor looks into and their eye, it is certainly valid to assume that there is frequent contact, even if accidental, resulting in force applied near the eye region. Awkward Posture: ● There is neck flexion at an angle far greater than the 15 degrees that would be considered comfortable. Environmental Factors: ● The procedure is often performed at a hospital. Operating/examination rooms often feature bright, acute lights for precise illumination. ● Hospitals are also kept fairly cold to control for humidity and bacterial growth. This answer requires outside information. Question: What is the role of risk assessment in human-centered design, improving task safety and tool usability? Moreover, what does it tell us about the relationship between affordance and design? Answer: Risk assessment is a crucial part of the design process as it helps engineers identify and mitigate hazards associated with a system (product or task). It involves evaluating the ergonomic factors within a task and the cognitive aspects of how the task is performed. Finally, the importance of affordances lies in the iterative process of design. We can re-design a tool or task by assessing risks and reducing or avoiding injuries. Group 2 A worker in a ping pong ball factory works an 8 hour shift with two 30 minute breaks scheduled in. They must squeeze each ping pong ball that comes off the assembly line to check that there are no leaks. The worker squeezes 10 balls with a pinch grip every 17 seconds, with each squeeze lasting 1 second. There is 15º of wrist extension during the squeeze. The worker has been performing this job for 11 years, and rates their exertion as a 2/10. Is this task dangerous for the worker? (HINT: use the Revised Strain Index) ANSWER: RSI with I = 0.2, E = 35.3, D = 1, P = 15º extension, h = 7

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