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Section III · Topic guide

Energy, work & power (physics essentials)

Section III — Sciences · a free, hand-written guide with worked reasoning and adaptive practice that finds your weak spots.

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The short answer

The handful of physics relationships that unlock a chunk of Section III.

Written and checked by GAMSAT tutors — not AI-generated.

Free interactive lesson

Try the reasoning style

Section I · Humanities & Social SciencesIllustrative example

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.

How to reason to the answer

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.

You don't need a physics degree for Section III — you need a handful of relationships and the confidence to rearrange them. Energy, work and power are the highest-yield ones.

The four you must own

Work: W = F × d · Kinetic energy: KE = ½mv² · Gravitational PE: PE = mgh · Power: P = W / t (energy per second). Units: energy and work in joules (J), power in watts (W = J/s).

CrashCourse — Work, Energy and Power (~10 min).

The shortcut most people miss

Conservation of energy often beats long kinematics. Energy just changes form — so the PE a falling object loses becomes the KE it gains: mgh = ½mv². No need for time or acceleration.

Worked example

A 2 kg ball is dropped from 5 m. Ignoring air resistance, how fast is it going just before it hits the ground? (g = 10 m/s²)

Check yourself

Two motors each do 6000 J of work. Motor A takes 2 s; motor B takes 6 s. Which is more powerful, and by how much?

Key takeaways

  • Know W = Fd, KE = ½mv², PE = mgh, P = W/t cold.
  • Energy is conserved — it changes form, it isn't lost.
  • mgh = ½mv² skips past time and acceleration.
  • Power is energy per second (watts = joules/second).

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4 min read · Concept