Human Factors, Ergonomics and Occupational Safety

Introduction

Industrial engineering is concerned not only with machines, materials, and methods, but also with the people who design, operate, maintain, inspect, and manage production systems. A technically efficient process can still produce poor results if it causes excessive fatigue, awkward postures, misunderstanding, unsafe actions, or unacceptable exposure to hazards. Human factors and ergonomics provide the scientific basis for designing work systems that fit human capabilities and limitations.

Ergonomics is the discipline concerned with understanding interactions among people and other elements of a system, and applying theory, principles, data, and methods to optimize human well-being and overall system performance. Human factors is often used broadly for the study of human capabilities, behavior, and performance in relation to system design. In industrial practice, the terms overlap substantially.

Occupational safety complements ergonomics by preventing injury, illness, property damage, and harmful events. Ergonomics commonly addresses gradual exposure, such as repetitive motion or sustained force, while safety engineering also addresses acute events such as entanglement, falls, explosions, and unexpected machine movement. The two fields should be integrated rather than managed separately.

Learning Objectives

After studying this chapter, students should be able to:

1. Explain the relationship between human factors, ergonomics, productivity, quality, and safety.
2. Apply anthropometric and biomechanical principles to workstation and tool design.
3. Evaluate cognitive demands, human–machine interfaces, workload, fatigue, and environmental conditions.
4. Identify hazards and assess risk using a structured process.
5. Apply the hierarchy of controls and explain the role of safety-management systems.
6. Recommend practical, ethical, and legally defensible improvements to work systems.

1. The Human-Centred Industrial Work System

A work system consists of people, tasks, tools, machines, information, physical surroundings, organizational arrangements, and outputs. Performance is an emergent property of their interaction. When an operator makes an error, the immediate cause may be an incorrect action, but the underlying causes may include ambiguous displays, poor training, unrealistic production targets, inadequate maintenance, or a badly designed procedure.

A useful systems perspective distinguishes three outcomes:

• Human well-being: health, safety, comfort, dignity, and sustainable workload.
• System performance: productivity, reliability, quality, flexibility, and maintainability.
• Organizational resilience: the capacity to anticipate, respond to, and learn from changing conditions.

These outcomes are usually complementary. For example, reducing unnecessary reaching can lower musculoskeletal risk while also reducing cycle time and variation. Conversely, forcing workers to bypass guards or procedures in order to meet a target is a sign of poor system design, not merely poor individual discipline.

Ergonomic design follows an iterative process:

1. Understand the users, tasks, constraints, and operating context.
2. Measure or estimate physical, cognitive, and environmental demands.
3. Identify mismatches between demands and human capabilities.
4. Generate and compare design alternatives.
5. Test alternatives with representative users.
6. Implement, monitor, and improve the design.

2. Anthropometry and Workstation Design

Anthropometry is the measurement of human body dimensions. It includes structural dimensions, such as standing height, and functional dimensions, such as reach distance during a task. Anthropometric data vary with sex, age, ethnicity, occupation, clothing, posture, and population. Designers must therefore use data from a population that resembles the intended users.

2.1 Percentiles and design decisions

A percentile describes the percentage of a reference population whose measured value is less than or equal to a specified value. It does not describe an individual’s percentage of body size. The design percentile depends on the purpose of the dimension.

The “design for the extremes” rule is not universal. A doorway requires clearance for large users, whereas a frequently used control should be reachable by small users. For many workstations, adjustability is superior to selecting a single percentile.

A simplified design relation for a required clearance is:

Here, C_required is the required clearance, D_p is the selected body dimension at percentile p, and the remaining terms represent clothing, movement, and safety allowances. All terms must use the same length unit. The relation is a design condition, not a statistical law; allowances must be established from the task and applicable standards.

2.2 Reach, posture, and adjustability

Controls should be placed within the normal reach envelope whenever possible. Frequently used controls should be closer than infrequently used controls, and emergency controls should be conspicuous, rapidly accessible, and protected against accidental activation.

Work height depends on the task. Precision work generally requires a higher surface to support visual attention, whereas heavy manual work may require a lower surface to permit force application through the arms and trunk. A single fixed height rarely suits all users and tasks. Adjustable tables, platforms, fixtures, and seats can improve fit, but adjustment mechanisms must be simple, durable, and easy to maintain.

A workstation assessment should consider:

• seated and standing alternatives;
• leg, knee, and foot clearance;
• visual line of sight;
• reach frequency and distance;
• posture during loading, inspection, and recovery;
• access for maintenance and cleaning;
• gloves, protective clothing, and footwear;
• variation in user stature and physical capability.

2.3 Anthropometric design limitations

Body dimensions are not independent. A person with a short stature may not have proportionally short arms, and static dimensions do not predict dynamic reach precisely. Furniture and tools should therefore be tested with users rather than designed solely from tables. Anthropometric data also require careful governance: data collection must respect privacy, informed consent, and appropriate use of demographic information.

3. Biomechanics and Manual Work

Biomechanics applies principles of mechanics to the human body. It helps engineers evaluate posture, force, motion, repetition, and duration. The aim is not to calculate an exact injury threshold for every worker, because injury risk is influenced by individual variation, tissue condition, fatigue, recovery, and psychosocial factors. Biomechanical analysis is best used to compare designs and prioritize controls.

3.1 Moments and external load

When a force acts at a distance from a joint, it creates a moment:

M is the moment in newton-metres (N·m), F is force in newtons (N), and d⊥ is the perpendicular distance from the joint axis to the force line in metres (m). The equation assumes a quasi-static situation and a clearly defined rotation axis. Dynamic acceleration, multiple forces, and three-dimensional movement require a more complete analysis.

For a simple horizontal lifting model, the low-back moment may be approximated as:

where W_load and W_trunk are gravitational forces in newtons, and h_load and h_trunk are their perpendicular moment arms in metres. This simplified model ignores muscle geometry, acceleration, load asymmetry, and support from other body segments. It is useful for demonstrating why holding a load farther from the body increases spinal demand.

Worked example. Suppose a 150 N component is held 0.40 m in front of a joint. The external moment is:

If the component is moved to 0.20 m, the moment becomes 30 N·m, assuming the force remains unchanged. The reduction is achieved without reducing the component mass; it results from reducing the moment arm.

3.2 Principles for reducing physical risk

The most effective interventions usually change the task rather than instructing workers to “lift correctly.” Useful measures include:

• reducing object mass or using smaller containers;
• keeping loads close to the body;
• reducing horizontal reach and twisting;
• using lift tables, hoists, conveyors, manipulators, or powered carts;
• improving handles and coupling surfaces;
• reducing repetition through automation or task redesign;
• allowing adequate recovery and job variation;
• storing heavy items between approximately knee and shoulder height where feasible.

A neutral posture is not a single rigid angle. It is a posture in which joint deviation, muscle effort, and tissue stress are reasonably low and can be sustained without excessive fatigue. Extreme flexion, extension, twisting, vibration, and static contraction should be minimized.

3.3 Repetition, force, and vibration

Musculoskeletal risk generally increases when force, repetition, awkward posture, duration, and insufficient recovery occur together. Screening tools such as the Rapid Entire Body Assessment (REBA), Rapid Upper Limb Assessment (RULA), and the NIOSH lifting equation can support assessment, but they do not replace professional judgment or worker consultation.

The revised NIOSH lifting equation uses a recommended weight limit (RWL):

The load constant LC is 23 kg under the equation’s defined reference conditions. The multipliers HM, VM, DM, AM, FM, and CM account respectively for horizontal location, vertical location, travel distance, asymmetry, frequency, and coupling. The lifting index is:

where L is the actual load in kilograms. The equation applies to selected two-handed lifting tasks under its stated assumptions; it should not be applied indiscriminately to one-handed lifting, pushing, pulling, seated lifting, highly variable tasks, or conditions outside its validated scope. A value of LI greater than 1 indicates that the task warrants attention; it is not a precise probability of injury.

4. Cognitive Ergonomics and Human–Machine Interaction

Cognitive ergonomics addresses perception, attention, memory, decision-making, mental workload, learning, and human error as they affect interactions with systems. In manufacturing, these issues arise in control rooms, CNC interfaces, maintenance procedures, inspection stations, alarms, material-handling equipment, and digital work instructions.

4.1 Mental models and situation awareness

A mental model is a person’s internal understanding of how a system works. Interfaces should support an accurate mental model through consistent labels, visible system status, understandable cause-and-effect relationships, and feedback after actions. Situation awareness involves perceiving relevant information, understanding its meaning, and anticipating what may happen next.

Poor designs create mode errors. For example, the same button may perform different actions depending on an invisible operating mode. A safer design makes the current mode visible, uses distinct controls where consequences differ, and requires confirmation for high-consequence actions.

4.2 Human error and defenses

Human error can be classified in several practical ways:

• Slip: the intention is appropriate but the action is incorrect.
• Lapse: a memory or attention failure, such as omitting a step.
• Mistake: the plan or decision is inappropriate for the situation.
• Violation: a deliberate departure from a rule, often influenced by production pressure, unclear procedures, or perceived impracticality.

This classification should not be used to assign blame automatically. A systems investigation asks why the action was likely, what barriers failed, and how the system can be made more tolerant of error. Common error-tolerant features include interlocks, keyed connectors, poka-yoke devices, checklists for critical steps, clear alarm priorities, and fail-safe states.

4.3 Display and control design

Good displays present information in a form suited to the decision. Analog trends can help users detect rate and direction of change; digital values can support precise readings. Colors should not be the only means of coding because users may have color-vision deficiencies, lighting may vary, and colors can have different cultural interpretations. Text, shape, position, and sound can provide redundant coding.

Alarms should be prioritized, informative, and actionable. An alarm that is frequent, ambiguous, or impossible to resolve encourages alarm fatigue. Each important alarm should answer, as far as practical: What happened? How serious is it? What should the operator do? What happens if no action is taken?

5. Fatigue, Workload, and Environmental Conditions

Fatigue is a reduced capacity to perform mental or physical work, often accompanied by reduced alertness, slower reaction, impaired judgment, and increased variability. It may result from long duration, high workload, sleep loss, shift work, heat, vibration, monotonous tasks, emotional stress, or inadequate recovery.

Fatigue risk management should address both the task and the schedule. Useful measures include appropriate staffing, realistic cycle times, planned breaks, job rotation that genuinely changes the loaded body region or cognitive demand, control of overtime, forward-rotating shifts where appropriate, and education about sleep and commuting risk. Breaks are not a substitute for eliminating excessive demand.

Environmental factors should be assessed as interacting exposures rather than isolated checklist items:

• Noise: can impair communication, mask alarms, cause hearing damage, and increase stress. Engineering controls include enclosure, isolation, damping, maintenance, and quieter equipment; hearing protection is a later line of defense.
• Lighting: should support visual demands while minimizing glare, reflections, flicker, and excessive contrast. Illuminance requirements depend on the task and applicable standards.
• Thermal conditions: heat stress depends on air temperature, radiant heat, humidity, air movement, clothing, workload, and acclimatization. Controls include shielding, ventilation, cooling, hydration, work–rest planning, and medical monitoring where necessary.
• Vibration: hand–arm and whole-body vibration can affect comfort, circulation, musculoskeletal health, and performance. Controls include low-vibration equipment, maintenance, isolation, exposure reduction, and suitable seating or handles.
• Indoor air quality and chemicals: substitution, enclosure, local exhaust ventilation, monitoring, and appropriate respiratory protection should be considered using the hierarchy of controls.

Environmental measurements must be interpreted against applicable legal exposure limits and recognized technical standards. A numerical measurement without knowledge of duration, frequency, calibration, and exposure criteria can be misleading.

6. Occupational Hazard Identification and Risk Assessment

A hazard is a source or situation with potential to cause harm. Risk combines the likelihood of an unwanted event or exposure with the severity of possible harm. Risk assessment is a structured process, not merely a numerical score.

A typical process is:

1. Define the task, equipment, people, and operating conditions.
2. Identify hazards during normal, abnormal, startup, shutdown, cleaning, maintenance, and emergency states.
3. Identify who may be exposed, including contractors, visitors, young workers, and people with disabilities.
4. Determine existing controls.
5. Estimate risk using a transparent method.
6. Select additional controls.
7. Implement, verify, and review the result after change or incident.

A simple qualitative matrix may classify risk using severity and likelihood categories. If a numerical method is used, a common representation is:

where R is a prioritization score, S is a defined severity rating, and L is a defined likelihood rating. The score is not a physical quantity and has no universal units. The categories and decision thresholds must be documented; multiplying ordinal labels does not produce a true probability.

Hazard identification methods include workplace inspection, job safety analysis, task observation, worker interviews, incident and near-miss analysis, safety data review, fault-tree analysis, what-if analysis, and failure mode and effects analysis (FMEA). Each has strengths and limitations. For example, FMEA is systematic for component or process failures, while observation may reveal workarounds that formal documents omit.

Figure: The hierarchy of controls, showing the preference for eliminating hazards before relying on personal protective equipment.

7. The Hierarchy of Controls and Safety Management

The hierarchy of controls ranks interventions by their expected reliability and independence from individual behavior:

1. Elimination: remove the hazard entirely.
2. Substitution: replace it with a less hazardous material, process, or method.
3. Engineering controls: isolate people from the hazard through guards, enclosures, interlocks, ventilation, or automation.
4. Administrative controls: change procedures, schedules, training, supervision, signage, or access rules.
5. Personal protective equipment (PPE): protect the worker with clothing or equipment.

PPE remains important, but it depends on selection, fit, availability, maintenance, correct use, and human tolerance. It should not be used to justify leaving a reasonably practicable higher-level control absent.

Machine safety requires attention to point-of-operation hazards, nip points, rotating parts, stored energy, unexpected startup, access during maintenance, and control-system failure. Guards and interlocks should be designed so that production incentives do not make bypassing them attractive. Lockout/tagout or an equivalent energy-isolation procedure is essential where hazardous energy may be released.

A safety-management system typically includes leadership commitment, worker participation, hazard identification, legal compliance, competence, operational controls, emergency preparedness, incident learning, auditing, and continual improvement. Standards such as ISO 45001 provide a management-system framework, while national laws, machinery regulations, exposure limits, and technical standards determine specific obligations. Organizations must consult current local requirements rather than treating a general textbook as legal advice.

8. Ethical, Legal, and Organizational Considerations

Safety is an ethical responsibility as well as a compliance requirement. Employers should not transfer foreseeable design risks to workers through warnings alone. Workers should be involved in risk assessment because they possess practical knowledge of variability, workarounds, discomfort, and near misses. Consultation must be meaningful and must not expose workers to retaliation.

Important governance principles include:

• protect personal health and anthropometric data;
• avoid discriminatory assumptions about ability or demographic group;
• provide reasonable accommodation where practicable;
• ensure contractors receive equivalent hazard information and controls;
• report incidents honestly, including near misses and unsafe conditions;
• distinguish accountability from blame;
• verify that productivity metrics do not reward unsafe shortcuts.

Digital monitoring and AI can support ergonomic assessment through posture estimation, wearable sensors, fatigue alerts, predictive maintenance, and analysis of near-miss data. However, these technologies raise concerns about privacy, surveillance, algorithmic bias, false alarms, cybersecurity, and responsibility for decisions. AI outputs should be treated as decision support, validated under real operating conditions, and reviewed by competent people. A camera-based posture score, for example, may miss load weight, recovery time, individual condition, or the reasons a worker adopts a posture.

9. Illustrative Case: Redesigning a Manual Assembly Cell

Background

The following is a fictional illustrative case. A small-machine assembly cell requires operators to retrieve components from bins, fasten four bolts, inspect the assembly, and place the product on a conveyor. Operators work eight-hour shifts with short cycle times. Reports show shoulder discomfort, occasional dropped components, and rising rework.

Problem definition

Observation reveals that heavy bins are stored below knee height, fasteners are located behind the operator, and the electric driver has a stiff trigger. Operators frequently twist, reach beyond the normal envelope, and support the driver with an elevated shoulder. The inspection light produces glare, and an alarm from a nearby machine is frequently ignored because it occurs many times per shift.

Analysis

The team conducts worker interviews, posture observations, a task-based risk assessment, and a review of rework records. A simplified moment calculation shows that moving a 120 N component from a 0.35 m reach to a 0.20 m reach reduces the external moment from 42 N·m to 24 N·m, assuming the same force and rotation axis. The analysis also identifies cognitive risks: the alarm is not prioritized, and the work instruction uses a similar icon for two different fastening modes.

Solution

The redesign includes:

• a height-adjustable fixture and sloped gravity-feed bins;
• positioning heavy components near the body and between knee and shoulder height;
• a balanced electric driver with a lower trigger force;
• a torque-controlled tool with visible completion feedback;
• a rotating fixture to reduce trunk twisting;
• improved, glare-controlled task lighting;
• a distinct icon and color-independent label for each fastening mode;
• alarm rationalization so that urgent alarms are distinguishable from advisory messages;
• scheduled micro-recovery opportunities and rotation to a less physically demanding inspection task;
• worker training and a follow-up measurement plan.

Outcome

After a trial period, the team records fewer extended reaches, lower observed shoulder elevation, fewer dropped components, and improved first-pass quality. The result is not attributed to one intervention alone. It reflects the combined effect of engineering redesign, improved information, worker participation, and management of workload.

Learning points

1. Ergonomic improvements can improve quality and productivity as well as health.
2. A hazard assessment must include normal production, maintenance, and abnormal conditions.
3. Cognitive and physical demands often interact.
4. Worker participation reveals practical problems that drawings and procedures may miss.
5. Outcomes should be verified with exposure measures, health indicators, quality data, and worker feedback.

10. Implementation, Verification, and Continuous Improvement

A professional ergonomic or safety intervention should specify the problem, affected population, baseline evidence, proposed controls, responsible persons, resources, and verification criteria. Useful indicators include exposure duration, force or posture measures, near misses, injury trends, absenteeism, quality defects, downtime, and worker-reported discomfort. No single indicator is sufficient.

Verification asks whether the control exists, is used, and actually reduces risk. Validation asks whether it performs under realistic conditions, including production peaks, maintenance, new operators, and foreseeable misuse. Management of change is essential whenever equipment, layout, materials, staffing, software, or schedules change.

The strongest improvement culture treats incidents and near misses as information about system performance. Investigations should seek failed barriers and contributing conditions rather than stopping at statements such as “operator was careless.” Corrective actions should be specific, assigned, time-bound, and checked for effectiveness.

Challenges and Limitations

Ergonomic assessment contains uncertainty. Anthropometric databases may not represent the workforce; observational scores simplify complex exposures; risk matrices can create false precision; and injury outcomes may appear long after exposure. Productivity pressures can also undermine controls, particularly when administrative measures are used without engineering support.

There is no universally safe posture, lifting weight, or work duration independent of context. Individual health conditions require professional assessment, and occupational health decisions should not be made from a textbook formula alone. Standards and legal requirements vary by jurisdiction and change over time. Consequently, engineers must combine quantitative tools with competent judgment, worker consultation, medical and safety expertise, and continual review.

Chapter Summary

Human factors and ergonomics integrate knowledge of human physical and cognitive capabilities into the design of work systems. Anthropometry supports decisions about clearance, reach, work height, seating, and adjustability, but data must match the intended population and be tested with real users. Biomechanics explains how force, distance, posture, repetition, and duration affect physical demand; the moment relation M = F × d⊥ demonstrates why reducing reach can reduce joint loading.

Cognitive ergonomics addresses mental workload, situation awareness, interface design, alarms, mental models, and human error. Fatigue and environmental exposures such as noise, heat, lighting, vibration, and air contaminants must be managed through a combination of engineering, organizational, and personal controls. Hazard identification and risk assessment should cover routine and non-routine work and should involve those who perform the work.

The hierarchy of controls prioritizes elimination, substitution, engineering controls, administrative controls, and PPE, in that order. Effective safety management combines leadership, participation, competence, operational control, emergency planning, incident learning, auditing, and continual improvement. Ethical practice requires respect for worker dignity, privacy, inclusion, and the principle that unsafe system design should not be disguised as individual failure. Ergonomic design is therefore both a technical discipline and a responsibility for sustainable, reliable, and humane industrial performance.

Key Terms

Anthropometry: Measurement and study of human body dimensions.

Biomechanics: Application of mechanical principles to the human body.

Cognitive ergonomics: Study of mental processes and their interaction with systems.

Clearance: Space provided to allow a person, body part, tool, or movement to pass safely.

Fatigue: Reduced physical or mental capacity resulting from exertion, insufficient recovery, or other demands.

Hazard: Source or situation with potential to cause harm.

Hierarchy of controls: Ordered framework prioritizing elimination and other controls over PPE.

Human factors: Study of human capabilities, behavior, and system interaction.

Human–machine interface: Means by which a person receives information from and controls a machine.

Likelihood: Defined estimate or category describing the chance of an event or exposure.

Moment: Rotational effect of a force about an axis, calculated in a simple case as force times perpendicular distance.

Musculoskeletal disorder: Injury or disorder affecting muscles, tendons, nerves, joints, or related tissues.

Percentile: Position of a measurement within a reference population distribution.

Personal protective equipment: Equipment worn or used to reduce exposure to a hazard.

Risk: Combination of the likelihood and severity of harm.

Situation awareness: Perception, understanding, and anticipation of relevant conditions.

Slip: Incorrect action despite an appropriate intention.

Substitution: Replacement of a hazard with a less hazardous alternative.

Workload: Physical or cognitive demands imposed by a task over time.

Review Questions

Short Answer Questions

1. Distinguish between a hazard and a risk.
2. Why are different percentiles used for reach and clearance design?
3. Define a slip, lapse, mistake, and violation.
4. State the five levels of the hierarchy of controls.
5. Why should worker participation be included in ergonomic assessment?

Long Answer Questions

1. Explain how anthropometry, adjustability, and task analysis should be combined when designing a workstation.
2. Discuss the biomechanical significance of force distance from a joint and describe methods for reducing manual-handling risk.
3. Explain how display design, alarm management, and mental models affect human–machine interaction.
4. Describe a complete occupational risk-assessment process for a machine-maintenance task.
5. Compare engineering, administrative, and PPE controls, including their advantages and limitations.

Analytical / Application Questions

1. An operator holds a 100 N tool 0.30 m from the elbow. A redesigned support reduces the distance to 0.15 m. Calculate both external moments using M = F × d⊥ and explain the practical significance.
2. A workstation requires frequent access to a control, but the smallest intended operator cannot reach it without leaning. Propose an assessment and redesign strategy using anthropometry, adjustability, and human–machine interaction principles.
3. A factory has repeated minor hand injuries despite training and mandatory gloves. Analyze why the existing approach may be inadequate and propose controls using the hierarchy of controls, including verification measures.

Multiple Choice Questions with Answers

Question 1

Which anthropometric design principle is most appropriate for a doorway clearance?

A. Accommodate a small user near the 5th percentile

B. Accommodate a large user, with appropriate allowances

C. Use the population mean only

D. Design for the shortest operator

Correct Answer: B. Accommodate a large user, with appropriate allowances

Question 2

A 150 N force acts 0.40 m from a joint axis. What is the simple external moment?

A. 37.5 N·m

B. 60 N·m

C. 150.4 N·m

D. 375 N·m

Correct Answer: B. 60 N·m

Question 3

Which control is highest in the hierarchy of controls?

A. Personal protective equipment

B. Administrative procedure

C. Elimination

D. Warning sign

Correct Answer: C. Elimination

Question 4

A worker intends to select the correct control but presses an adjacent control instead. This is best classified as a:

A. Slip

B. Lapse

C. Mistake

D. Violation

Correct Answer: A. Slip

Question 5

What is a major limitation of a qualitative risk score calculated as severity times likelihood?

A. It always gives a probability in percent

B. It has no need for defined categories

C. It can create false precision when ordinal ratings are multiplied

D. It cannot be used to prioritize actions

Correct Answer: C. It can create false precision when ordinal ratings are multiplied

Question 6

Which intervention most directly reduces a low-back moment during lifting, assuming load force is unchanged?

A. Move the load farther from the body

B. Increase twisting speed

C. Reduce the perpendicular distance to the joint

D. Reduce lighting at the workstation

Correct Answer: C. Reduce the perpendicular distance to the joint

Question 7

Which feature best supports situation awareness?

A. Hidden operating modes

B. Consistent feedback and visible system status

C. One alarm tone for every condition

D. Controls that change function without indication

Correct Answer: B. Consistent feedback and visible system status

Question 8

Why is personal protective equipment generally ranked below engineering controls?

A. PPE is never useful

B. PPE depends more heavily on correct individual selection, fit, and use

C. Engineering controls require no maintenance

D. PPE eliminates the hazard at its source

Correct Answer: B. PPE depends more heavily on correct individual selection, fit, and use

Question 9

Which activity is essential after implementing an ergonomic control?

A. Assume the control works permanently

B. Remove worker involvement

C. Verify that it is used and actually reduces exposure

D. Replace all measurements with training records

Correct Answer: C. Verify that it is used and actually reduces exposure

Question 10

A 120 N load is held 0.35 m from a joint. If the distance is reduced to 0.20 m, what is the new simple moment?

A. 24 N·m

B. 60 N·m

C. 120.20 N·m

D. 600 N·m

Correct Answer: A. 24 N·m