Teacher: One page per learner, printed A4. Sections <b>A</b> and <b>B</b> count toward <b>Written Works</b>; see <code>assessment.md</code> §1. Item <b>★</b> is the diagnostic and is the book on the table — the guide's own second example, and the one most of the class will get wrong. The key below is screen-only and will not print.
A Write the partner in full — always in the form <em>A pushes B</em>
The force
Its partner
The person pushes the boat backwards
The hammer hits the nail
The Earth pulls the mango down
The swimmer pushes the water backwards
The wheel pushes backwards on the road
B Pair, or not a pair — and name the object each force acts on
The two forces
Object of force 1
Object of force 2
A pair?
Earth pulls book down · table pushes book up
Person pushes boat · boat pushes person
Earth pulls lamp down · cord pulls lamp up
Magnet A pulls B · B pulls A
C Equal forces, unequal motion — two learners on chairs push off each other
What I saw happen
Why equal forces did that
The two boxes are the same size on purpose. Describing the motion correctly and explaining it correctly are separate achievements.
D Tug of war — one sentence each
How big is Team A's pull on the rope compared with Team B's? <span class="blank"></span>
So what decides who wins? <span class="blank lg"></span>
Would the answer change if Team A were much heavier? <b>Why?</b> <span class="blank lg"></span>
★ The challenge — the book on the table
A book rests on a table. Write the two forces acting <b>on the book</b>. <span class="blank lg"></span> <span class="blank lg"></span>
Are those two an action–reaction pair? <span class="blank"></span> <b>How do you know?</b> <span class="blank lg"></span>
Write the <b>true partner</b> of each of those two forces. <span class="blank lg"></span> <span class="blank lg"></span>
Answer key — screen only, not printed.
<b>A</b> · the boat pushes the person forwards · the nail pushes back on the hammer · the mango pulls the Earth up · the water pushes the swimmer forwards · the road pushes the wheel forwards. <b>An answer that does not name both objects scores nothing</b>, however right it sounds — naming both is the method.<br><b>B</b> · book / book / <b>no</b> · boat / person / <b>yes</b> · lamp / lamp / <b>no</b> · B / A / <b>yes</b>.<br><b>C</b> · the lighter learner moves further and faster; the forces were equal but the masses were not, so the accelerations differed.<br><b>D</b> · exactly equal · the friction between each team's feet and the ground · a heavier team has more friction available, so mass helps — but not by making their pull on the rope bigger.<br><b>★ This is the diagnostic.</b> Item 1: the Earth pulls the book down (its weight); the table pushes the book up. Item 2: <b>no</b> — both act on the book, so they are a balanced pair. Item 3: the book pulls the Earth up; the book pushes the table down. <b>A learner who answers "yes" to item 2 has equal-and-opposite without the two-object rule</b>, and it is the single most common error in this competency at every level, including among adults who studied physics.