This packet is everything a parent or guide needs to assess Unit 07 at home — learning targets, the answers that count as correct, the mastery rubric, calibration examples, and a clipboard score sheet. No multiple-choice test: the student shows mastery by predicting where a loaded meter stick balances and then verifying it.
By the end of the Torque & Rotational Motion unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Predict a balance point; verify it on a meter stick.
The student explains why a skater spins faster with arms in (Page 4).
Distances, torque balance, and result kept distinct.
You are making a decision, not adding up points. For each criterion, decide whether the work is Not yet, Approaching, or Mastered — the column language tells you which. A criterion counts as mastered only when the student can both predict the balance and defend it from the torques. A student carries three tokens per term; one token buys a re-do of one criterion on another day, so a single bad afternoon never sinks the unit.
Accept any answer in the synonyms column — they are pre-approved as equivalent. The third column flags the confusions that look close but are not yet, so you can coach precisely.
| Canonical answer | Accepted synonyms | Common confusion / discriminator |
|---|---|---|
| Torque & balance | ||
| Torque | moment of force | Force times lever arm — where the force acts matters, not just its size |
| Lever arm | moment arm | The perpendicular distance from the pivot to the line of force |
| Pivot | fulcrum / axis | The axis you take torques about; choose it to simplify the problem |
| Rotational equilibrium | balanced torques | Net torque and net force both zero — neither spins up nor accelerates |
| Rotation | ||
| Rotational inertia | moment of inertia | Depends on how mass is distributed, not just how much |
| Angular momentum | spin momentum | Conserved when no external torque acts; pull mass in and spin rises |
| Angular velocity | spin rate | How fast it turns; increases as rotational inertia decreases |
| Center of mass | balance point | The point where weight effectively acts |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Torque | Thinks only the size of the force matters, not where it acts. | Uses force times distance but ignores the angle or lever arm. | Calculates torque as force times lever arm, accounts for direction, and explains why a longer wrench is easier. |
| Rotational equilibrium | Cannot set up a balance condition. | Balances torques but forgets to also balance forces. | Solves static-equilibrium problems by setting net torque and net force to zero about a chosen pivot. |
| Rotational inertia | Thinks only total mass matters, not its arrangement. | Knows shape matters but cannot compare two objects. | Explains that rotational inertia depends on how mass is distributed and ranks objects that roll or spin accordingly. |
| Angular momentum | Does not recognize a rotational analog to momentum. | Names angular momentum but cannot apply conservation. | Applies conservation of angular momentum to explain spin-up and spin-down when the radius changes. |
| Lab technique (balance / rotational inertia) | Balances by trial and error with no measurement. | Measures distances but does not predict the balance point first. | Uses a meter-stick balance to predict and then verify equilibrium, reporting the result with uncertainty. |
| Integration (cross-domain) | Treats the science as isolated facts; makes no cross-domain connection. | Names a link to history, reading, or writing but cannot defend why it matters. | Connects the unit to its anchor across History · Reading · Writing (plus chosen electives) and defends why the connection matters. |
The split between Approaching and Mastered is lever arm: a mastered student weighs distance as much as force. Ask “a small mass far out balances a big mass close in — why?”
Read these before you grade. They show what Mastered and Not yet actually sound like, plus the edge cases where you should coach rather than decide on the spot.
Student: ______________________________________ Date: _______________ Guide: _________________________
| # | Criterion | Decision | Notes |
|---|---|---|---|
| 1 | Torque | NY / Appr / Mast | |
| 2 | Rotational equilibrium | NY / Appr / Mast | |
| 3 | Rotational inertia | NY / Appr / Mast | |
| 4 | Angular momentum | NY / Appr / Mast | |
| 5 | Lab technique (balance / rotational inertia) | NY / Appr / Mast | |
| 6 | Integration (cross-domain) | NY / Appr / Mast |
☐ No ☐ Yes — for criterion: __________ Tokens remaining: ☐ 3 ☐ 2 ☐ 1 ☐ 0
NY = Not yet · Appr = Approaching · Mast = Mastered · Unsure between two levels? Circle the lower one and note what a re-do would need.