The short answer
Free-body diagrams, F = ma, and the action–reaction trap — the core of GAMSAT mechanics.
Written and checked by GAMSAT tutors — not AI-generated.
Try the reasoning style
We treat forgetting as a failure — a lapse to be patched with reminders and records. Yet a mind that kept everything could not think; it would drown in the undifferentiated noise of every moment it had ever lived. To forget is not so much to lose information as to decide, mostly without our noticing, what was never worth keeping.
The author's argument relies most directly on which unstated assumption?
Pick an option to see how the tutor reasons to the answer — not just whether you were right.
Not quite — the answer is B.
Work backwards from the conclusion: a mind that ‘kept everything’ supposedly ‘could not think.’ That only follows if thinking means leaving most of experience out — so B is the premise the argument quietly rests on. A raises reliability, which the passage never weighs; C contradicts ‘mostly without our noticing’; D smuggles in a claim about intellect the passage never makes. The question rewards finding the hidden premise, not recalling a fact.
Almost every mechanics question comes down to one habit: draw a free-body diagram, then apply . If the object isn't accelerating, the forces balance (); if it is, the net force points the way it accelerates.
Newton's three laws, briefly
1st (inertia): no net force → constant velocity (including at rest). 2nd: . 3rd: every force has an equal, opposite reaction — on a different object.
The action–reaction trap
Newton's third-law pairs act on two different objects, so they never cancel on the same object. The book on a table: gravity pulls the book down and the table pushes the book up — those are not a third-law pair (both act on the book). The book also pushes down on the table — that's the partner to the table's push.
Solving any forces problem
1. Draw the free-body diagram
One dot for the object; arrows for every force acting ON it (weight, normal, tension, friction, applied).
2. Pick axes and resolve
Align one axis with the motion (along a slope, use along/perpendicular). Split angled forces into components.
3. Apply F = ma per axis
Sum forces along each axis. Set perpendicular = 0 if there's no motion that way; the motion axis gives the acceleration.
Worked example
A 2 kg block is pushed along a frictionless floor by a constant 10 N horizontal force. What is its acceleration? Then: what is the normal force from the floor? (g = 10 m/s²)
Check yourself
A car accelerates forward. By Newton's third law, the tyres push backward on the road with force F. What is the equal-and-opposite partner to that force?
Key takeaways
- Always start with a free-body diagram of the forces ON the object.
- F_net = ma. No acceleration ⇒ forces balance (F_net = 0).
- Resolve angled forces into components; align an axis with the motion.
- Third-law pairs act on DIFFERENT objects and never cancel on one object.
- Normal force isn't always mg — it adjusts to whatever keeps perpendicular motion zero.
Practise this with real GAMSAT-style questions
Free account: a timed diagnostic, an AI tutor that explains every answer, essay marking on the official rubric, and a plan built around your weak spots.