Murray State University · Part four · Example projects

Engineering Trivia — Should Have Known That

Murray State University
Demo 11 of 17 · Part four · Engineering · Stage 1

Drag first. Trust your gut.

Which of the numbers an engineer is supposed to carry around can you actually place by feel?

Before you start. Thirty-five numbers here are scored by percent error — how close your guess sits to the true value on an ordinary ruler. A slider forces a number out of you before you can hedge with "I don't know," and a guess you committed to is what makes the correction stick.

Predict

Drag the slider to where you think each number sits, before you can see how close you were.

Try

Press LOCK IT IN to reveal the true value and see the size of your miss.

Takeaway

A confident guess you commit to is what makes a correction stick — a shrug does not.

Sourced the value you are about to guess

Linear estimates

Thirty-five questions across five categories, scored by percent error — pick your length and categories below.

Check yourself

A code says A36 steel's yield strength is 250 MPa (36 ksi). Is that the average strength a real A36 beam tests at?

Item 10 in the bank — think back to your guess before picking.

Bryant Harrison · Murray State University
One HTML file · runs offline

Guidehow to use this demo

Forty numbers an engineer is expected to carry without looking up — can you place them by feel?

Where this sits: Part four's example projects apply an AI-built classroom tool with its goal, engine and assumptions all one tap away — this one is a calibration game for number sense.

  1. Linear estimates. Pick your length, categories and mode, then press Start linear estimates; drag the slider and press Lock it in for each question.
  2. Log estimates. Unlocks once stage 1 is complete — five questions that span orders of magnitude, scored differently on purpose.
  3. Debrief. Unlocks once stage 2 is complete — final scores and the linear-vs-log comparison.

Getting around

The stage tabs switch stages, but stages 2 and 3 stay locked until you have played the one before — the tabs stay visible so you can see the whole route. Details opens the evidence and sources for the current stage. Guide reopens this card; Settings has Open Presenter Notes, Presentation mode and Reset.

Time

A 10-question linear round plus the 5-question log round runs about 15–20 minutes with discussion; solo or 2–4 team pass-and-play on one device.

Settings

Presenter notes

The printable session plan, on screen.

Presentation mode

Scales the page up one notch for projecting to a room, and puts a Notes button in the header.

Reset

Back to stage 1's setup screen: no game in progress, every category on, solo mode, stages 2 and 3 re-locked, and both check cards cleared. Presentation mode stays as you set it.

DetailsLinear estimates

What is live

Every value is a citation; the scoring is computed here

Live your guess, the band and the points

The slider position, the percent-error calculation, the band you land in, and the points you earn are all computed in your browser the moment you lock in a guess.

Sourced all 35 linear values below

Every number in this stage is a published reference value, a defined constant, a code requirement, or an exact unit conversion — not a measurement this page performs. 19 of the 35 ship with a qualifier because a single number would otherwise stand in for a typical value, a real range, a specified minimum, or a design convention; 8 of the 35 are also scored against the range the item itself names rather than against a single point (the reveal still shows the one anchor value). These counts are derived from the question bank at build time.

How it works

error = |guess − true| / true  ·  bands at 5% / 15% / 35% / 60%

Percent error is the fraction your guess misses the true value by. Below 5% is Bullseye (100 pts); past 60% is Way Off (0 pts). The full table is in the printable guide.

Assumptions and simplifications

  • Every value is a typical or reference figure for its category, not a measurement of one specific real object — a real beam, a real cord, a real gallon will differ, sometimes by a lot, depending on grade, brand, or conditions.
  • Several values are design conventions fixed by a code rather than physical averages (steel's E = 200 GPa, concrete's 150 pcf design weight, A36's 36 ksi minimum yield) — using the code number is correct engineering practice, but it is a different kind of "true" than a measured physical constant, which is exactly what each item's qualifier says.
  • Slider endpoints are chosen to be wide enough not to give the answer away; they are not themselves a claim about the plausible range of the true value.
  • Where an item carries an accepted range, a guess inside it scores Bullseye and a guess outside it is measured from the nearer edge of the range, not from the anchor — so the score never punishes an answer the item's own text endorses. The ranges are listed under Sources below, each with the page it came from.

Sources

    Boundary: this stage does not claim any value is a single, universal physical constant unless its qualifier is empty — a qualifier present means the real world carries a range, a floor, or a code dependency that one slider cannot show.

    Presenter Notesthe printable guide, on screen

    Teacher and presenter guide · Slider-based estimation trivia for engineering number sense

    Engineering Trivia — Should Have Known That

    Demo 11 of 17 · Part four, Example projects · 15–20 minutes

    You need: index.html open in any modern browser, phone or projector. No network, no install, no accounts. Nothing is fetched at runtime, so it works with the wi-fi off.

    Learning goals

    One per stage, in the learner's own words — these are the three Takeaway cards on screen, verbatim.

    1. A confident guess you commit to is what makes a correction stick — a shrug does not.
    2. On a log scale, the order of magnitude is most of the answer — and item 23's rule-of-thumb number is a single point standing in for a whole risk curve.
    3. A ranged or code-defined number is still worth a confident guess — precision and truth are not the same thing.

    Where this sits on the path

    An AI-built classroom tool from Part four: its goal is number-sense calibration, its engine is a live-scored slider running entirely on the device, and its assumptions — which of its 40 values are single facts versus ranges, minimums, or code conventions — are one tap away in each stage's Details drawer.

    One question for the session

    "If you had to bet, not guess — how close is your gut, really, to the numbers you already use?"

    Stage 1 · Linear estimates

    Question. Which of the numbers an engineer is supposed to carry around can you actually place by feel?

    Predict. Drag the slider to where you think each of 35 numbers sits, before the truth is revealed.

    Activity (timed beats). 0–2 minPick a length (5/10/15), categories, and solo or teams; play the first one yourself, wrong on purpose, to set the tone. 2–10 minPoll before every lock-in if presenting to a room: hands up for higher, hands up for lower, then press LOCK IT IN. Read the "because…" line aloud after each reveal.

    Expected observation. The band badge (Bullseye/Close/Warm/Cold/Way Off) and the "you vs. truth" markers on the track; the observation cue names the band and the miss size.

    Check-yourself answer key. "It's a specified minimum — real steel usually tests higher" is correct; "it's the average strength" is the flawed model item 10 exists to break.

    Teaching limit. A linear slider only works while the plausible answers fit on one linear track — which is exactly what breaks in stage 2, where the right answer to the resistivity item would sit at step 0 of 1,000. Note also that eleven items are scored against a stated range (the reveal names it): a guess inside the range is Bullseye, and the reveal's single "truth" is the anchor, not the only acceptable answer.

    Stage 2 · Log estimates

    Question. When a guess can be off by a factor of ten, does the exact digit even matter?

    Predict. Commit to a power of ten first, on all five log-scale items (resistivity, the speed of light, the cardiac-fibrillation current, the static-shock voltage, and AA battery energy).

    Activity. 10–14 minPlay all five; ask the room to say a power of ten out loud before each lock-in rather than a specific number.

    Expected observation. A big absolute miss can still land Bullseye if the order of magnitude is right — the opposite of stage 1's intuition.

    Check-yourself answer key. "No — 100 mA is one point on a risk curve, not a safety line" is correct; treating 40 mA as automatically safe because it is under 100 mA is the refutation item's flawed model.

    Teaching limit. The game cannot show WHY the curve looks the way it does (current × duration × path) — only that a single number understates it. The Details drawer names the shape; it does not re-derive IEC 60479-1's curve.

    Stage 3 · Debrief

    Question. Were your log guesses or your linear guesses closer?

    Predict. Guess which deck scored higher before reading the comparison.

    Activity. 14–18 minRead the linear-vs-log average aloud; debrief from the "should have known that" card — ask that team or student what they thought the number was and why. The wrong mental model is more useful than the right answer.

    Expected observation. An average-points comparison computed live from this session's own answers — nothing here is precomputed.

    Teaching limit. Five log questions is a small sample; one lucky or unlucky guess swings that average far more than the 35-question linear average moves. Say this out loud before reading the comparison as if it were a strong result.

    18–20 minPlay again from the debrief, or ⚙ → Reset for a clean start between class periods.

    Misconceptions this bank can leave, refuted

    Misconception: "100 mA is the safe/unsafe line for shock." It is a rule-of-thumb anchor on a current×duration×path curve (IEC 60479-1); sustained exposure carries meaningful fibrillation risk from well below 100 mA. Item 23's qualifier and stage 2's refutation check both name this directly — it is the single highest-stakes item in the bank.
    Misconception: "A36's 250 MPa is what the steel actually measures." It is ASTM A36/A36M's specified MINIMUM; real mill-certified steel commonly tests higher. Stage 1's check item exists to break exactly this substitution of a floor for a fact.
    Misconception: "7¾ in risers are the code, full stop." That figure is the IRC's residential cap; the IBC's general means-of-egress cap is 7 in, and only Exception 3 for dwelling units raises it to match. Carrying the residential number into a commercial context applies the wrong code to the wrong building type.
    Misconception: "13 A is safe for any 16-gauge extension cord." NEC Table 400.5(A)(1) sets 13 A by conductor count and ambient temperature, not length; a widely used practical derating guide drops well below 13 A for a long cord run. The bank's own factoid already warns a 1,500 W heater is close to the derated limit — a long cord makes it worse, not the same.

    Discussion prompts

    1. 62.4 lb/ft³ and 0.433 psi/ft are the same fact. Ask the room to derive one from the other (62.4 ÷ 144 in²/ft²).
    2. Which number is the dangerous one — 100 mA across the chest, or the few thousand volts (2,000–4,000 V for most people) it takes to feel a static shock? It is the current, not the voltage, that kills; say plainly that 100 mA is a rule of thumb, not a safe/unsafe line.
    3. Why not build everything out of aluminum? Young's modulus 200 vs. 70 GPa; density 7,850 vs. 2,700 kg/m³. Both ratios are about 2.9, so stiffness-to-weight is nearly identical — the real choice is cost, buckling, and joining.
    4. What if steel and concrete expanded at different rates? Every summer would crack the building — reinforced concrete works on an approximate coincidence, not an exact one.
    5. A36 is named after its own answer — the 36 is the specified minimum yield strength in ksi. How many other "memorized" numbers are printed on the spec sheet's name, and how many of those are minimums rather than typicals?
    6. A single number can be right AND still teach the wrong lesson. Every one of the 40 values in this bank checks out against a real source — but 23 of them ship with a qualifier because a bare number would have implied more precision than the world actually has, and 11 of the 40 are scored against a range rather than a point for the same reason. Ask the room to name one more everyday "fact" that is really a range, a floor, or a design convention.
    7. One gallon of gasoline is 33.7 kWh — roughly a full day of an average US home's electricity, and (per this build's re-sourcing) a genuinely accurate figure for real gasoline, not a lowball regulatory number.
    8. Why did the log questions go so badly (or so well)? Because they are not recall questions — getting the size of the number right is the actual skill.
    Reading a Way Off: a Way Off on a linear question is a fact the student does not have. A Way Off on a log question means they do not know what size the answer is — say the difference out loud; it is the most transferable idea in the game.

    How it is scored

    Thirty-five linear questions score on percent error; five log questions (stage 2) score on decades off — |log10(guess/true)|.

    BandLinearLogPts
    Bullseyewithin 5%1.26×100
    Closewithin 15%2.1×75
    Warmwithin 35%5×40
    Coldwithin 60%16×10
    Way Offpast thatpast that0

    Because both scales share this one point table, stage 3's linear-vs-log comparison uses average points per question rather than the raw percent/decades numbers, which are not directly comparable. The debrief also prints the control — what a randomly placed slider would average on the questions actually played, scored over all 1,001 positions — and across the whole bank that control is within a few points of equal on the two decks, so a gap between a student's two averages is knowledge, not a gentler deck.

    Where an item carries an accepted range (its qualifier or reveal text names it, and the Details drawer lists it with its source), a guess inside the range scores Bullseye and a guess outside it is measured from the nearer edge. Eleven items are scored this way; the other 29 score against their single value exactly as the table above describes.

    Editing the question bank

    The bank now lives in src/data.js (moved out of index.html for this retrofit) — each entry carries id, category, prompt, units, value, min/max, scale ("linear"/"log"), factoid, an optional qualifier, an optional band: [lo, hi], and a source object (name, url, fetched, optional also list for a second citation). Edit src/data.js, then run node build.js — the build derives the qualifier and band counts from the bank and refuses to run until this guide, the README and demo.json state the same numbers. A value with no qualifier is presented as a single, unhedged fact — add one whenever a new question is really a range, a specified minimum, or a code/edition-dependent figure, and add a band only where a sourced range for the same quantity already appears in the item's own text, per the standing "research, not memory" rule: back it with an actual source before shipping it, or mark it unverified.

    Presenter controls

    • ⚙ Settings holds Open Presenter Notes (this guide), Presentation mode (projector-sized type), and Reset (back to stage 1's setup screen, both later stages re-locked, presentation mode left as you set it).
    • Stage tabs switch stages; stages 2 and 3 stay locked until the stage before them is played through — the tabs stay visible so the room sees the whole route.
    • Details (in each stage's intro) opens that stage's sources, formula, assumptions, and boundary statement.
    • Keys: Enter/Space lock in a guess and advance the reveal; Esc closes any open dialog.

    Sources (session-fetched, not recalled)

    Every one of the 40 taught values carries its own citation in the app's Details drawer (per stage); this is the standards-body / primary-source subset, re-checked for this retrofit rather than carried over from memory:

    The full 40-row table (value, qualifier, source, date checked) is in src/data.js and in this retrofit's return report; some lower-stakes items (exact unit conversions, defined SI constants) are cited to a well-established secondary reference (Engineering ToolBox, Wikipedia quoting a standard's own language, AmesWeb material tables) where the underlying standard itself is paywalled (ASTM, AISC, ACI) — named by designation in the app's Details drawer either way.

    Engineering Trivia (Should Have Known That) · Bryant Harrison · Murray State University · Offline single-file web game. Open index.html to play. src/demo-guide.html is the canonical source of this document; the shipped teacher-guide.html, the PDF beside it, and the in-app presenter notes are all generated from it at build time.

    Open the printable copy (teacher-guide.html) — the same document, laid out for print; the PDF beside it is a render of that file.
    Bryant Harrison · Murray State University