This packet is everything a parent or guide needs to assess Unit 05 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 measuring the momentum of colliding carts and testing whether it is conserved.
By the end of the Momentum & Collisions unit, a student should be able to:
Six criteria, each judged Not yet / Approaching / Mastered (Page 3).
Measure momentum before and after a collision; test conservation.
The student explains what is conserved in each collision (Page 4).
Velocities, momentum totals, and comparison 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 take the measurement and defend what is conserved. 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 |
|---|---|---|
| Momentum & impulse | ||
| Momentum (p) | mass × velocity | A vector — direction matters; distinct from kinetic energy |
| Impulse | force × time | Equals the change in momentum; a longer contact time softens the collision |
| Conservation of momentum | total momentum stays constant | Holds for an isolated system; an external force breaks it |
| Isolated system | no net external force | Only then is the total momentum conserved |
| Collisions | ||
| Elastic collision | kinetic energy conserved | Momentum and kinetic energy are both conserved |
| Inelastic collision | kinetic energy lost | Momentum is conserved; kinetic energy is not |
| Perfectly inelastic | objects stick together | One shared final velocity; the most kinetic energy is lost |
| Two-dimensional momentum | component-wise conservation | Conserve each direction (x and y) independently |
| Criterion | Not yet | Approaching | Mastered |
|---|---|---|---|
| Momentum & impulse | Confuses momentum with force or energy. | Computes momentum but not the impulse–momentum connection. | Relates impulse to change in momentum and explains why a longer contact time softens a collision. |
| Conservation of momentum | Does not recognize when momentum is conserved. | Applies conservation but drops the vector directions. | Applies conservation to isolated systems as a vector equation and defends why external forces would break it. |
| Elastic vs. inelastic collisions | Assumes energy is always conserved in a collision. | Knows the difference but cannot say what is conserved in each. | Distinguishes elastic from inelastic collisions and states precisely what is conserved in each. |
| Two-dimensional momentum | Cannot handle momentum off a straight line. | Splits into components inconsistently. | Resolves momentum into components and conserves each direction independently. |
| Lab technique (collision carts) | Measures one cart and ignores the other. | Measures both but does not compare total momentum before and after. | Uses collision carts and timers to measure total momentum before and after and tests conservation 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 what is conserved: momentum is conserved in every collision, but kinetic energy only survives an elastic one. Ask “is this elastic or inelastic, and what is conserved?”
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 | Momentum & impulse | NY / Appr / Mast | |
| 2 | Conservation of momentum | NY / Appr / Mast | |
| 3 | Elastic vs. inelastic collisions | NY / Appr / Mast | |
| 4 | Two-dimensional momentum | NY / Appr / Mast | |
| 5 | Lab technique (collision carts) | 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.