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BEC JCE Design & Tech study materials
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BEC JCE Design & Tech practice questions

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Question 1Design process and problem solving

In a design process, what is the main purpose of writing a problem statement before generating ideas?

  1. To define the need, constraints, and success criteria that will guide later decisions Correct answer.
  2. To record the final specifications the client has already approved
  3. To list every possible solution the team may consider
  4. To estimate the manufacturing cost of the finished product

Explanation

A problem statement frames the design work by stating who has the need, what constraints apply, and how success will be judged. It comes before idea generation so that concepts can be evaluated against agreed criteria rather than personal preference.

Question 2Design process and problem solving

A team builds a simple physical model to test whether a folding mechanism jams. Which kind of model is this?

  1. A focus group
  2. A morphological chart
  3. A design brief
  4. A functional prototype Correct answer.

Explanation

A functional prototype reproduces the working behaviour of a concept so that its performance can be observed and measured. Testing whether a mechanism jams is a functional question about motion and interference, so a working model is the appropriate tool.

Question 3Design process and problem solving

Which activity best describes brainstorming as used in engineering design?

  1. Selecting the single best concept by scoring it against weighted criteria
  2. Documenting the final design for regulatory approval
  3. Generating many ideas quickly while deferring judgement to a later stage Correct answer.
  4. Testing a prototype against the original specification

Explanation

Brainstorming deliberately separates idea generation from evaluation so that quantity and variety come first. Criticism during the session suppresses contributions, so judgement is postponed until ideas can be screened systematically.

Question 4Design process and problem solving

During evaluation, a team scores concepts against criteria such as cost, safety, and ease of use, giving each criterion a different weight. What does this weighting represent?

  1. The number of team members who voted for each criterion
  2. The measurement uncertainty of each concept's score
  3. The relative importance of each criterion to the project's success Correct answer.
  4. The order in which criteria were first suggested

Explanation

Weights express how much each criterion matters when the overall merit of a concept is calculated. A heavily weighted criterion such as safety can dominate the result even if other criteria score higher in raw terms.

Question 5Design process and problem solving

What distinguishes a constraint from a criterion in a design specification?

  1. A constraint is a limit that must be met, while a criterion is a goal used to compare options Correct answer.
  2. A constraint changes during the project, while a criterion stays fixed
  3. A constraint is set by the designer, while a criterion is set by the user
  4. A constraint applies only to cost, while a criterion applies only to appearance

Explanation

Constraints are non-negotiable boundaries such as legal limits or maximum dimensions that any acceptable solution must satisfy. Criteria are desirable qualities that concepts are judged against, so trade-offs between them are allowed.

Question 6Design process and problem solving

A designer studies how users actually prepare meals in their own kitchens before proposing a new appliance. Which approach does this describe?

  1. Failure modes and effects analysis
  2. Reverse engineering of a competitor
  3. Tolerance analysis of parts
  4. Observation of users in context Correct answer.

Explanation

Watching real users in their own environment reveals unmet needs and workarounds that interviews alone may miss. This contextual observation feeds directly into defining the design problem and its requirements.

Question 7Design process and problem solving

What is the purpose of a morphological chart in concept generation?

  1. To record customer complaints received after launch
  2. To rank finished concepts by their calculated manufacturing cost
  3. To combine sub-solutions for different functions into new overall concepts Correct answer.
  4. To schedule design reviews across the project timeline

Explanation

A morphological chart lists the functions a product must perform and the alternative means for each function. Selecting one means per function produces combinations, some of which become novel overall concepts.

Question 8Design process and problem solving

Why is iteration a normal part of a well-run design process?

  1. It ensures the project schedule never needs to change
  2. Earlier assumptions are tested and refined as new evidence becomes available Correct answer.
  3. It guarantees the first concept will be the one finally produced
  4. It removes the need to document decisions along the way

Explanation

Design decisions rest on incomplete information, so testing and feedback reveal where earlier assumptions were wrong. Revisiting requirements and concepts lets the team converge on a better solution instead of defending an early guess.

Question 9Design process and problem solving

A team must choose between two concepts. Concept P scores 7 on durability and 4 on cost, while Concept Q scores 5 on durability and 8 on cost, where higher cost scores mean lower cost. Durability is weighted twice as heavily as cost. Which concept wins on the weighted total?

  1. Concept P, with a weighted total of 18 against 18 for Q, decided by the durability score Correct answer.
  2. Concept Q, with a weighted total of 21 against 20 for P
  3. Concept Q, with a weighted total of 18 against 16 for P
  4. Concept P, with a weighted total of 22 against 21 for Q

Explanation

Weighting durability at 2 and cost at 1 gives P a total of 2x7 + 4 = 18 and Q a total of 2x5 + 8 = 18. The totals tie, so the tie-break falls to the more heavily weighted criterion, durability, where P leads.

Question 10Design process and problem solving

A design team uses a decision matrix and finds that the top two concepts score within one point of each other. What is the most appropriate next step?

  1. Average the two concepts into one design without further analysis
  2. Investigate the criteria where the scores diverge and gather better evidence before committing Correct answer.
  3. Discard both concepts and begin a completely new ideation round
  4. Select the higher-scoring concept immediately because the matrix is objective

Explanation

A small score difference is usually within the uncertainty of subjective ratings, so the matrix alone cannot justify a decision. Examining which criteria drive the gap shows where additional testing or user input would be most informative.

Question 11Design process and problem solving

A prototype fails during testing when a joint cracks under load. What is the most useful immediate response in the design process?

  1. Declare the concept proven because the failure was not catastrophic
  2. Remove the load case from the test plan so the prototype passes
  3. Increase the marketing budget to compensate for the delay
  4. Identify the failure mechanism and revise the joint before retesting Correct answer.

Explanation

A test failure is information about where the design is inadequate, and its value lies in diagnosing the mechanism. Understanding why the joint cracked allows a targeted change that can then be verified by repeating the test.

Question 12Design process and problem solving

A team applies failure modes and effects analysis to a new valve. They assign a high severity rating but a very low occurrence rating to one failure mode. How should this combination be interpreted?

  1. The consequence would be serious if it happened, but it is not expected to happen often Correct answer.
  2. The failure is impossible and can be ignored entirely
  3. The ratings contradict each other and one must be an error
  4. The failure is frequent but harmless when it occurs

Explanation

Severity rates how bad the effect of a failure would be, while occurrence rates how likely that failure mode is to arise. The two dimensions are independent, so a severe but rare failure is a coherent and common result.

Question 13Design process and problem solving

Which situation best calls for building a low-fidelity prototype rather than a high-fidelity one?

  1. The team wants fast feedback on overall form and layout before investing in detail Correct answer.
  2. The product must survive a drop test to a published standard
  3. Engineers need to measure the fatigue life of the final alloy
  4. The client requires production-representative materials for certification

Explanation

Low-fidelity prototypes are cheap and quick, which suits early exploration where the questions concern broad form and arrangement. Precision measurement and certification require high-fidelity models made from representative materials.

Question 14Design process and problem solving

A design brief states that a new lamp must cost no more than 20 currency units to make and must use only recyclable materials. How should these statements be classified?

  1. Both are constraints because they set limits any acceptable design must satisfy Correct answer.
  2. The cost limit is a criterion and the material rule is a constraint
  3. The cost limit is a constraint and the material rule is a criterion
  4. Both are criteria because they are desirable rather than mandatory

Explanation

Each statement sets a boundary that a compliant design cannot exceed, which is the defining property of a constraint. Criteria, by contrast, are qualities traded off against one another rather than fixed limits.

Question 15Design process and problem solving

A team uses a pairwise comparison matrix to weight design criteria. What does this method produce?

  1. Relative weights derived from how often each criterion is preferred over the others Correct answer.
  2. An absolute cost estimate for each design concept
  3. A ranked list of users by their importance to the project
  4. A list of failure modes ordered by severity

Explanation

Pairwise comparison asks which of two criteria matters more, repeated across all pairs, and counts the wins to derive relative weights. The result is a consistent weighting scheme that can feed a decision matrix.

Question 16Design process and problem solving

A designer uses a computer-aided design model to check whether a proposed assembly can be serviced without removing neighbouring parts. What is the main benefit of this approach?

  1. It removes the need to define requirements at the start
  2. It replaces the need for any physical testing of the product
  3. Access and clearance problems can be found before any physical parts are made Correct answer.
  4. It guarantees the assembly will meet its cost target

Explanation

Digital assembly models let engineers check reach, clearance, and sequence of operations cheaply while changes are still easy. Finding such conflicts before tooling exists avoids costly rework later in the project.

Question 17Design process and problem solving

During concept screening, a team keeps a deliberately simple reference concept in the comparison set. What role does this reference serve?

  1. It provides a familiar baseline against which relative strengths and weaknesses are judged Correct answer.
  2. It is the concept the team has already decided to manufacture
  3. It is included only to make the matrix look complete
  4. It represents the least expensive option available

Explanation

A reference concept, often an existing product, anchors the ratings so that assessors share a common standard. Without such a baseline, scores drift between raters and comparisons become unreliable.

Question 18Design process and problem solving

A design review is held at the end of the concept phase. Which outcome indicates the review has served its purpose?

  1. Agreement to postpone all decisions until manufacturing begins
  2. A longer list of open questions than existed before the review
  3. Documented decisions on which concepts proceed and which are dropped, with reasons Correct answer.
  4. A verbal consensus that is not recorded anywhere

Explanation

A design review exists to examine progress against requirements and to make decisions that move the project forward. Recording which concepts continue and why preserves the rationale for later stages and audits.

Question 19Design process and problem solving

A team wants to reduce the environmental impact of a product across its whole life. Which design strategy addresses the widest range of life-cycle stages?

  1. Adding extra packaging to protect the product in transit
  2. Designing for disassembly so materials can be separated and recovered at end of life Correct answer.
  3. Increasing the number of unique fasteners to speed assembly
  4. Choosing a glossier surface finish to improve shelf appeal

Explanation

Designing for disassembly affects material recovery, recycling quality, and the effort needed at end of life, so it touches several life-cycle stages at once. Options that only affect appearance or packaging have a much narrower influence.

Question 20Design process and problem solving

A client keeps adding new requirements after the concept has been frozen. Which project practice best protects the design process from uncontrolled change?

  1. Refusing all changes for the remainder of the project
  2. A formal change-control process that assesses the impact of each request before acceptance Correct answer.
  3. Accepting every request immediately to keep the client satisfied
  4. Hiding the change requests from the engineering team

Explanation

Change control evaluates each request for its effect on cost, schedule, and technical risk before the team commits. This keeps the specification stable while still allowing justified changes to be made deliberately.

Question 21Design process and problem solving

A team sets a target that a device must operate for 500 hours between services. Which requirement quality does this target demonstrate?

  1. It is a constraint on appearance rather than performance
  2. It is aspirational, so it cannot be checked
  3. It is a preference that users may ignore
  4. It is measurable, so compliance can be verified by test Correct answer.

Explanation

A well-formed requirement states a quantity and the conditions under which it applies, so a test can confirm whether it is met. The 500-hour figure makes the requirement verifiable rather than a vague aspiration.

Question 22Design process and problem solving

A team ranks five concepts and finds that the third-ranked concept has a much lower estimated manufacturing cost than the top two. Cost carries a weight of 0.4 in the matrix. What is the most defensible action?

  1. Ignore the cost advantage because the matrix has already produced a ranking
  2. Choose the third-ranked concept because cost always outweighs other criteria
  3. Re-examine the weightings and the cost estimates to confirm the ranking is robust before deciding Correct answer.
  4. Discard the matrix and decide by seniority of team members

Explanation

A strong showing on a heavily weighted criterion can overturn a small lead elsewhere, so the result deserves scrutiny. Checking the weights and the reliability of the cost data shows whether the ranking reflects genuine advantage or input error.

Question 23Design process and problem solving

A prototype passes its verification tests, but field trials show users consistently misuse a control. How should the team interpret this result?

  1. The verification tests were invalid and should be discarded
  2. The design meets its written requirements but fails the underlying user need, so the requirements should be revisited Correct answer.
  3. The users are at fault, so no design change is warranted
  4. The product is complete because verification is the only measure of success

Explanation

Verification confirms that a design meets its stated requirements, while validation confirms that it satisfies real user needs. A product can pass verification yet fail validation, which signals that the requirements themselves were incomplete.

Question 24Design process and problem solving

Two failure modes in a risk analysis have the same product of severity, occurrence, and detection. One is a gradual wear-out mode and the other is a sudden failure with no warning. Why might the team still treat them differently?

  1. Gradual wear-out is always more dangerous because it lasts longer
  2. Detection ratings make severity irrelevant in every case
  3. Equal risk scores always require identical treatment under any risk method
  4. The sudden mode gives users no chance to respond, so its effective risk is higher despite the equal score Correct answer.

Explanation

Composite risk scores compress several dimensions into one number and can hide differences that matter operationally. A failure with no warning removes the opportunity for mitigation by the user, which raises its practical consequence.

Question 25Design process and problem solving

A team must decide whether to continue developing a concept or switch to an alternative. Early tests are encouraging but based on a small sample. Which reasoning best supports the decision?

  1. Switch because any uncertainty means the current concept will fail
  2. Estimate the cost of being wrong in each direction and gather more evidence where that cost is highest Correct answer.
  3. Delay all decisions until every possible test has been completed
  4. Continue because sunk development cost must always be recovered

Explanation

Under uncertainty, the value of further evidence depends on the consequences of choosing wrongly. Directing effort to the decision with the largest downside risk gives the greatest improvement in the eventual choice.

Question 26Design process and problem solving

Which statement best describes the role of a design brief at the start of a project?

  1. It specifies the supplier chosen for each purchased part.
  2. It documents the test results collected during verification.
  3. It records the agreed problem, constraints and success criteria for the work. Correct answer.
  4. It lists the final manufacturing tolerances for each component.

Explanation

A design brief is the front-end agreement that frames the problem: it states the need, the constraints, the target users and the criteria by which success will be judged. Later documents such as tolerance drawings, test reports and supplier lists belong to detailed design and production, not to the brief.

Question 27Design process and problem solving

A team is generating concepts and wants many varied ideas quickly without judging them. Which practice supports this goal?

  1. Recording every idea first and deferring criticism to a later session Correct answer.
  2. Limiting the session to ideas that already have proven patents
  3. Asking only the most senior engineer to contribute suggestions
  4. Applying a weighted decision matrix to each idea as it appears

Explanation

Divergent idea generation works best when evaluation is separated from creation, so participants build on each other's suggestions without fear of early rejection. Judging ideas while they are being produced suppresses quantity and variety, which are the raw material for later convergence.

Question 28Design process and problem solving

What distinguishes a functional requirement from a non-functional requirement in a specification?

  1. A functional requirement is written by the client, while a non-functional one is written by the manufacturer.
  2. A functional requirement describes what the system must do, while a non-functional one constrains qualities such as performance or reliability. Correct answer.
  3. A functional requirement can be tested, while a non-functional one can only be judged subjectively.
  4. A functional requirement applies only to software, while a non-functional one applies only to hardware.

Explanation

Functional requirements state the behaviours or functions the product must deliver, such as 'grind coffee to a selected coarseness'. Non-functional requirements set quality attributes and constraints, such as noise level, service life, weight or safety, and they too must be testable.

Question 29Design process and problem solving

A designer needs to understand the sequence of steps a nurse follows when preparing an intravenous drip. Which technique is most appropriate?

  1. A weighted decision matrix comparing competing concepts
  2. A tolerance stack-up calculation on the drip housing
  3. A bill of materials review for the disposable set
  4. A task analysis observing and breaking down the procedure step by step Correct answer.

Explanation

Task analysis decomposes an activity into its steps, decisions and information needs so that a design can support the real workflow. Decision matrices, tolerance calculations and parts reviews address concept selection, geometry and procurement rather than the user's procedure.

Question 30Design process and problem solving

A team writes the requirement 'the kettle must be easy to use'. Why is this requirement weak?

  1. It cannot be verified because it states no measurable criterion Correct answer.
  2. It duplicates a constraint already fixed by legislation
  3. It describes the manufacturing process instead of the product
  4. It specifies a material rather than a function

Explanation

A usable requirement must be verifiable, meaning there is an agreed test and a measurable threshold. 'Easy to use' gives no metric, so no one can demonstrate compliance; it should be restated with a measurable criterion such as successful first-time operation by a defined user group.

Question 31Design process and problem solving

During brainstorming a participant repeatedly interrupts to point out why each idea will fail. What is the most effective facilitator response?

  1. Ask the critic to justify each objection with data
  2. Remove the critical participant from the project team
  3. Park the objections on a visible list for later review and continue generating Correct answer.
  4. End the session and schedule a decision meeting instead

Explanation

Capturing concerns on a parking list respects the critic's input while preserving the separation between idea generation and evaluation. The objections are then examined systematically during the convergence phase, when evidence and criteria are available.

Question 32Design process and problem solving

A team maps each function of a new product against every available working principle in a grid. What is the main benefit of this representation?

  1. It calculates the manufacturing cost of each variant
  2. It systematically exposes combinations of principles that might otherwise be missed Correct answer.
  3. It fixes the final geometry of the product housing
  4. It ranks the concepts by customer preference

Explanation

A function-principle grid forces the team to consider every working principle for every function, so unusual pairings become visible and can be combined into new concepts. It is a divergent structuring tool; it does not fix geometry, cost or preference rankings.

Question 33Design process and problem solving

A design team must estimate the cost of a concept before any detailed drawings exist. Which approach is most defensible?

  1. Use the final supplier quotation for the concept
  2. Defer all cost consideration until production begins
  3. Apply parametric cost relationships derived from similar past products Correct answer.
  4. Assume the cost equals that of the previous product

Explanation

At concept stage, parametric or analogous estimating uses known cost drivers such as mass, part count or power from comparable products to give a defensible early figure with stated uncertainty. Quotations, arbitrary assumptions and deferral either are impossible at this stage or expose the project to late, costly surprises.

Question 34Design process and problem solving

A team wants to check whether a new hand tool fits a wide range of users. Which approach gives the most direct evidence?

  1. Building a physical mock-up and testing it with representative users Correct answer.
  2. Reading published anthropometric tables only
  3. Running a stress simulation on the tool's steel shaft
  4. Reviewing competitor sales figures for similar tools

Explanation

Fit and usability are revealed by having representative users handle a physical mock-up and perform realistic tasks, because grip, reach and comfort interact in ways tables alone cannot capture. Sales data, structural simulation and static dimension tables each address a different question.

Question 35Design process and problem solving

A design team wants to compare its concept against the best competing products on several criteria. Which tool is designed for this purpose?

  1. A benchmarking chart positioning the concept and rivals against shared criteria Correct answer.
  2. A Gantt chart scheduling the development tasks
  3. A fault tree analysing possible failure causes
  4. A tolerance analysis of the assembly

Explanation

Benchmarking places the concept and its competitors side by side against the same customer-relevant criteria, revealing where the concept leads or lags. Scheduling, failure analysis and tolerance work serve other purposes and do not compare competitive performance.

Question 36Design process and problem solving

A team is unsure whether a proposed mechanism will work at all. Which prototyping choice is most appropriate at this stage?

  1. A production-representative prototype in final materials
  2. A complete assembly built to final tolerances
  3. A focused physical or computational model that tests only the critical principle Correct answer.
  4. A full marketing mock-up with final graphics

Explanation

When the open question is whether a principle works, a focused model that isolates the critical mechanism answers it fastest and cheapest. Production-representative, marketing and fully toleranced builds are expensive and premature before the principle is proven.

Question 37Design process and problem solving

A team uses a decision matrix in which criteria weights sum to one. Concept A scores 6, 8 and 4 on criteria weighted 0.5, 0.3 and 0.2. What is Concept A's weighted score?

  1. 6.0
  2. 6.2 Correct answer.
  3. 5.2
  4. 4.8

Explanation

The weighted score is the sum of each score multiplied by its weight: 6×0.5 = 3.0, 8×0.3 = 2.4 and 4×0.2 = 0.8, which totals 6.2. Multiplying by weights that sum to one keeps the result on the same scale as the original ratings.

Question 38Design process and problem solving

Two concepts score almost identically in a decision matrix, but one relies on an unproven technology. How should the team interpret this result?

  1. Average the two concepts into a single design
  2. Abandon the project because the matrix gave no clear answer
  3. Choose the higher-scoring concept and ignore the technology risk
  4. Treat the scores as inconclusive and investigate the risk before deciding Correct answer.

Explanation

A near-tie means the criteria and scores lack the resolution to separate the options, and unproven technology carries uncertainty that the matrix may not capture. The sound response is to gather more evidence on the risky element, then rescore or apply a targeted test.

Question 39Design process and problem solving

A design process uses stage gates. What is the essential function of a gate review?

  1. To document the final manufacturing instructions
  2. To generate new concepts for the next phase
  3. To confirm that exit criteria are met before committing further resources Correct answer.
  4. To assign individual tasks to team members for the week

Explanation

A stage gate is a control point where predefined exit criteria are checked and a decision is made to proceed, pause, rework or stop. This prevents a project from carrying unresolved risk and cost into later phases where changes are far more expensive.

Question 40Design process and problem solving

A team discovers late in detail design that a key assumption from the concept phase was wrong. Which practice would most have reduced the cost of this discovery?

  1. Testing the critical assumption with a quick experiment during the concept phase Correct answer.
  2. Adding more reviewers to the final drawing check
  3. Freezing the design earlier to prevent changes
  4. Increasing the number of concepts generated at the start

Explanation

The cost of correcting an error rises sharply as a project advances, so critical assumptions should be tested as early and cheaply as possible. A quick experiment in the concept phase would have exposed the flaw while changes were still inexpensive, whereas freezing, extra drawing checks and more concepts do not address an untested assumption.

Question 41Materials and their properties

Which property describes a material's ability to be drawn into a thin wire without breaking?

  1. Brittleness
  2. Malleability
  3. Hardness
  4. Ductility Correct answer.

Explanation

Ductility is the capacity of a material to undergo tensile deformation and be stretched into wire form. Metals such as copper and gold are ductile because their crystal planes slide under tension. Malleability instead concerns flattening under compression, and brittleness concerns fracture with little deformation.

Question 42Materials and their properties

A material that returns to its original shape after a load is removed is said to behave in which way?

  1. Permanently
  2. Viscoelastically
  3. Elastically Correct answer.
  4. Plastically

Explanation

Elastic behaviour means deformation is fully recovered when the applied stress is removed, because atomic bonds return to their equilibrium spacing. Plastic deformation, by contrast, leaves a permanent change of shape. Viscoelastic materials show both elastic and time-dependent viscous responses.

Question 43Materials and their properties

Which class of material is characterised by a crystalline lattice of positive metal ions surrounded by a sea of delocalised electrons?

  1. Polymers
  2. Metals Correct answer.
  3. Ceramics
  4. Glasses

Explanation

The metallic bond consists of a regular array of cations held together by a shared cloud of free electrons. This delocalised electron sea explains the good electrical and thermal conductivity of metals and their ability to deform plastically. Ceramics and polymers have predominantly ionic, covalent, or van der Waals bonding instead.

Question 44Materials and their properties

In a stress-strain curve for a ductile metal, what does the area under the curve up to fracture represent?

  1. Young's modulus
  2. Toughness Correct answer.
  3. Poisson's ratio
  4. Yield strength

Explanation

Toughness is the energy absorbed per unit volume before fracture, which equals the area under the complete stress-strain curve. A tough material combines adequate strength with significant ductility. Young's modulus is the slope of the linear elastic region, and yield strength is a single stress value.

Question 45Materials and their properties

Which hardness test uses a 10 mm steel ball pressed under a load of 3000 kgf as its standard condition?

  1. Knoop
  2. Rockwell C
  3. Brinell Correct answer.
  4. Vickers

Explanation

The Brinell test presses a hardened steel or tungsten carbide ball, commonly 10 mm diameter, into the surface and measures the resulting indentation diameter. Vickers uses a diamond pyramid, Rockwell uses various diamond or ball indenters with depth measurement, and Knoop uses an elongated diamond.

Question 46Materials and their properties

What is the main reason ceramics are generally poor conductors of electricity at room temperature?

  1. They have very low melting points
  2. They always contain large amounts of water
  3. They contain too many free electrons
  4. Their electrons are tightly bound in ionic or covalent bonds Correct answer.

Explanation

In ceramics, valence electrons are localised in strong ionic or covalent bonds, leaving very few charge carriers free to move. Conduction therefore requires either high temperature to promote electrons across a wide band gap or the presence of mobile ions. This is why most ceramics act as insulators at ambient temperature.

Question 47Materials and their properties

Which term describes a polymer made from two or more different monomer species chemically combined in the chain?

  1. Oligomer
  2. Homopolymer
  3. Elastomer
  4. Copolymer Correct answer.

Explanation

A copolymer is formed when two or more distinct monomer types are polymerised together into the same chain. The arrangement may be random, alternating, block, or graft, and it allows properties to be tuned. A homopolymer uses only one monomer species.

Question 48Materials and their properties

A component must resist indentation and scratching in service. Which property should be specified?

  1. Thermal expansion
  2. Hardness Correct answer.
  3. Electrical resistivity
  4. Density

Explanation

Hardness quantifies resistance to localised plastic deformation, scratching, and wear. It is the property most directly linked to abrasion resistance in service. Density, thermal expansion, and resistivity describe unrelated physical behaviour.

Question 49Materials and their properties

A steel bar of original length 200 mm stretches by 0.4 mm under load. What is the engineering strain?

  1. 0.0002
  2. 0.002 Correct answer.
  3. 0.02
  4. 0.2

Explanation

Engineering strain equals change in length divided by original length, so 0.4 mm divided by 200 mm gives 0.002. Strain is dimensionless. Expressing it as 0.2 percent is equivalent, but the decimal value is 0.002.

Question 50Materials and their properties

A cylindrical specimen of diameter 10 mm carries an axial load of 15.7 kN. What is the approximate engineering stress?

  1. 200 MPa Correct answer.
  2. 50 MPa
  3. 100 MPa
  4. 500 MPa

Explanation

Cross-sectional area equals pi times radius squared, giving about 78.5 square millimetres for a 10 mm diameter. Dividing 15,700 N by 78.5 mm squared gives approximately 200 MPa. Stress is force divided by original area.