WCAS - Washington Comprehensive Assessment of Science Engineering Design and Solutions Questions and Answers — Questions and Answers
Question 1: An engineering team is designing a new commuter bicycle. The marketing department has specified that the bicycle must be priced under $400 and weigh less than 15 kg. The design will be considered successful if it achieves a durability rating of at least 8 out of 10 in stress tests. Which of the following is a design *constraint*?
- Achieving a durability rating of 8/10
- The color of the bicycle frame
- Weighing less than 15 kg (Correct answer)
- The number of gears it has
Correct answer: Weighing less than 15 kg
In engineering design, constraints are limitations or restrictions on the design, often related to resources, materials, or specific requirements that must be met. [9, 11] Weighing less than 15 kg is a specific, quantifiable limit the design must adhere to. Achieving a durability rating of 8/10 is a criterion, which is a standard for measuring the success or quality of the design. The color and number of gears are design choices, not fundamental constraints in this context.
Question 2: A student group has identified a problem: the classroom's recycling bin is often contaminated with non-recyclable trash. They have brainstormed several potential solutions. According to the engineering design process, what is the most logical next step?
- Build a prototype of the most complex solution to see if it works.
- Select the cheapest solution and implement it immediately.
- Create a final presentation of the chosen solution for the teacher.
- Establish criteria and constraints to evaluate the potential solutions. (Correct answer)
Correct answer: Establish criteria and constraints to evaluate the potential solutions.
After brainstorming, the next critical step in the engineering design process is to develop a clear set of criteria (measures of success) and constraints (limitations) for a solution. [1, 10] This framework is essential for systematically and objectively evaluating the brainstormed ideas to determine which one is most likely to be successful before committing resources to prototyping or implementation.
Question 3: Which of the following best defines a 'trade-off' in the context of engineering design?
- The process of building a physical model to test a potential solution.
- A design choice where improving one desired feature necessitates worsening another. (Correct answer)
- The final, optimized solution that is chosen for mass production.
- A situation where a design completely fails to meet any of the established criteria.
Correct answer: A design choice where improving one desired feature necessitates worsening another.
A trade-off is a fundamental concept in engineering design where a decision must be made to sacrifice one benefit to gain another. [7, 14] For example, making a product stronger (a benefit) might require using heavier materials, thus increasing its weight (a drawback). Engineers must constantly balance these competing criteria to find an optimal solution.
Question 4: A team is developing a device to purify water in remote areas. They have built an initial prototype. What is the primary purpose of building and testing this first prototype?
- To secure funding from investors for mass production.
- To identify flaws and gather performance data to inform the next design iteration. (Correct answer)
- To create the final, polished product ready for sale to consumers.
- To prove that their initial design concept is perfect and requires no changes.
Correct answer: To identify flaws and gather performance data to inform the next design iteration.
A prototype is an early model of a product built to test a concept or process. [2, 5] Its main purpose is to allow engineers to test functionality, identify weaknesses, and collect data that will guide improvements in the next version of the design. [3, 6] It is a key part of the iterative process of refining and optimizing a solution.
Question 5: An engineer is designing a new ski helmet. The primary criterion is safety, but other important criteria include low weight, comfort, and aerodynamics. The engineer finds that using a denser, thicker foam improves the safety rating significantly but also increases the helmet's weight and reduces its aerodynamic efficiency. This situation is a clear example of:
- A systematic failure in the design process.
- The need to make trade-offs between competing criteria. (Correct answer)
- The complete satisfaction of all design constraints.
- An error in the initial problem definition.
Correct answer: The need to make trade-offs between competing criteria.
This scenario perfectly illustrates the concept of a trade-off, which is central to engineering design. [13, 15] The engineer must balance the competing criteria of safety, weight, and aerodynamics. Improving one criterion (safety) has a negative impact on others (weight, aerodynamics). The final design will be a compromise that seeks to optimize the overall solution based on prioritized criteria.
Question 6: An engineering team has developed and tested three different prototypes for a new, inexpensive solar-powered lamp. The primary goal is to maximize brightness (measured in lumens) while keeping the cost under a $15 constraint. Which prototype should be selected for further development?
- Prototype A: 150 lumens, $12 cost.
- Prototype B: 200 lumens, $18 cost.
- Prototype C: 140 lumens, $14 cost.
- Prototype D: 180 lumens, $14 cost. (Correct answer)
Correct answer: Prototype D: 180 lumens, $14 cost.
The evaluation of a solution requires comparing performance against both criteria and constraints. [14, 15] The hard constraint is a cost under $15. Prototype B fails this constraint, so it must be eliminated. Of the remaining options (A, C, and D), the primary criterion is to maximize brightness. Prototype D provides the highest brightness (180 lumens) while still meeting the cost constraint ($14), making it the optimal choice.
