The GAMSAT physics formula sheet — with what each formula means
There's no formula sheet in the real exam — and no calculator. So alongside every relationship, this page gives you the plain-English reading and the mental-arithmetic habit that Section III reasoning actually runs on.
Motion & kinematics
Constant-acceleration problems are really bookkeeping: five quantities (u, v, a, s, t), each equation linking four of them. The skill is spotting which quantity the stem never mentions — that missing symbol picks the equation for you.
Velocity after time t
Final velocity v is the starting velocity u plus the velocity gained: acceleration a for time t.
In the exam: No displacement s in it — use it when the stem says nothing about distance.
Displacement under constant acceleration
Distance covered: what you'd travel at the starting speed, plus the extra from accelerating.
In the exam: From rest (u = 0) it collapses to s = ½at² — falling objects: ~5 m in the 1st second, ~20 m by two seconds (with g ≈ 10).
The no-time equation
Links speeds to distance directly, skipping time entirely.
In the exam: Doubling a drop height multiplies impact speed by √2, not 2 — a favourite proportional-reasoning trap shape.
Average velocity
Total displacement over total time.
In the exam: Under constant acceleration it also equals (u + v)/2 — often the fastest route to an answer.
Acceleration
How quickly velocity changes: the change in velocity divided by the time it took.
No-calculator habit: Take g as 10 m/s² unless told otherwise — the answer options are nearly always spaced far enough apart that the ~2% error cannot change your pick.
Forces & momentum
Force questions reward drawing the situation before touching any equation: what pushes, what resists, and which direction wins. Momentum questions are conservation questions — the total before equals the total after, and everything else is arithmetic.
Newton's second law
The net (unbalanced) force on a body equals its mass times its acceleration.
In the exam: Net force. If something moves at constant velocity, the net force is zero no matter how many forces act.
Weight
Weight is the gravitational force: mass times the gravitational field strength g.
In the exam: Mass doesn't change on the Moon; weight does. Stems that swap the two words are testing exactly this.
Momentum
Momentum is mass times velocity — a direction matters (vector) quantity.
Impulse
A force applied for a time changes momentum by exactly that product.
In the exam: Same momentum change, longer time → smaller force. This is why crumple zones, airbags and bending your knees on landing work.
Conservation of momentum
In a collision with no outside force, total momentum before equals total momentum after.
In the exam: If the bodies stick together, the right side becomes (m₁ + m₂)v — one unknown, one line of algebra.
Hooke's law
A spring's restoring force is proportional to how far you stretch or compress it (k is the stiffness).
In the exam: Linear until it isn't — a graph that departs from the straight line is showing you the elastic limit.
No-calculator habit: A 70 kg person weighs about 700 N (g ≈ 10). Anchoring one everyday value like that lets you sanity-check whether an answer is off by a factor of ten.
Work, energy & power
Energy is the great shortcut: when a problem looks like it needs the full motion story, energy conservation usually replaces it with one before/after comparison. Track where the joules went — that is the whole method.
Work done by a force
Work is force times the distance moved along the force's direction (θ is the angle between them).
In the exam: Carrying a bag horizontally does no work on it against gravity — the force is perpendicular to the motion.
Kinetic energy
The energy of motion: half the mass times speed squared.
Gravitational potential energy
Energy stored by lifting a mass m a height h against gravity.
In the exam: Only the height CHANGE matters — the path taken to get there doesn't.
Power
Power is how fast energy is transferred — work per unit time, or force times velocity when pushing at constant speed.
In the exam: Watts are joules per second. A 60 W device moves 60 J every second — unit reasoning like this answers many power stems alone.
Efficiency
The fraction of input energy that ends up doing what you wanted; the rest usually leaves as heat.
No-calculator habit: Kinetic energy scales with speed SQUARED: twice the speed is four times the energy, and three times the speed is nine. Say the scaling out loud before reaching for numbers.
Fluids & pressure
Fluid stems love physiology: blood pressure, IV drips, breathing. The physics underneath is three ideas — pressure is force spread over area, pressure grows with depth, and what flows into a pipe must flow out.
Pressure
Pressure is force divided by the area it acts on.
In the exam: Same force, smaller area, bigger pressure — needles and stiletto heels are the standard mental anchors.
Pressure at depth
Pressure at depth h in a fluid of density ρ: the surface pressure plus the weight of fluid above.
In the exam: Depth is all that matters — not the container's shape or width.
Buoyant force (Archimedes)
The upward force equals the weight of fluid the object displaces.
In the exam: Floats if the object's average density is below the fluid's; the fraction submerged equals the density ratio.
Continuity of flow
For an incompressible fluid, what enters a pipe each second must leave it: narrower cross-section, faster flow.
In the exam: This is why a narrowed artery means faster blood at the narrowing — the basis of many physiology-flavoured stems.
Flow through a tube (Poiseuille, proportionally)
At a fixed pressure difference, volume flow through a tube scales with the fourth power of its radius.
In the exam: Small radius changes, huge flow changes: narrow a vessel by 20% and flow drops to about 40% of what it was (0.8⁴ ≈ 0.41).
No-calculator habit: Radius appears to the FOURTH power in vessel-flow contexts: halving a vessel's radius cuts flow to one-sixteenth at the same pressure. Powers of two are your friend — halve and halve again.
Waves, sound & light
One relationship (v = fλ) plus proportional reasoning covers most wave stems. For light at boundaries, refraction follows one rule; for sound and radiation, intensity falling with the square of distance does most of the work.
Wave equation
Wave speed equals frequency times wavelength.
In the exam: In a given medium v is fixed, so frequency and wavelength trade off inversely.
Period and frequency
The period (time per cycle) is the reciprocal of frequency (cycles per second).
Inverse-square intensity
Intensity from a point source falls with the square of distance — the same energy spreads over a growing sphere.
In the exam: Applies to sound, light and radiation alike; it is the geometry, not the wave type, doing the work.
Refractive index
How much a medium slows light: the ratio of light's vacuum speed to its speed in the medium.
Snell's law
How light bends crossing a boundary between media of different refractive index.
In the exam: Into an optically denser medium (higher n): bends toward the normal. Remember the direction and half the refraction stems answer themselves.
The decibel scale
Decibels are logarithmic: every 10 dB step multiplies sound intensity by ten.
In the exam: So 30 dB is not 'three times' 10 dB — it is one hundred times the intensity. Log scales are a classic S3 reading trap.
No-calculator habit: Inverse-square drills: triple the distance, one-ninth the intensity. Run the scaling in whichever direction the stem asks before touching real numbers.
Electricity & circuits
Circuit stems reduce to two habits: V = IR applied to the right piece of the circuit (the whole loop or one component — never a mix), and knowing what stays the same in series (current) versus parallel (voltage).
Ohm's law
The voltage across a resistance equals the current through it times the resistance.
Electrical power
Three equivalent forms — pick the one whose quantities the stem actually gives you.
In the exam: I²R is why transmission lines run at high voltage: same power, less current, far less heating loss.
Charge
Charge moved is current times time — one amp is one coulomb per second.
Resistors in series
Resistances in a single path simply add; the same current passes through each.
Resistors in parallel
Parallel paths share the current; combined resistance is always LESS than the smallest branch.
In the exam: Adding a parallel path always lowers total resistance — a pure-logic check that needs no arithmetic at all.
No-calculator habit: Two equal resistors in parallel halve the resistance; in series they double it. Extreme-case checks like these catch wrong answers faster than solving the circuit.
Heat & gases
Thermal stems are accounting problems (where did the joules go?), and gas stems are ratio problems — fix what's constant, then let PV = nRT tell you how the rest must move.
Heating a substance
Heat needed = mass × specific heat capacity × temperature change.
In the exam: Water's high c is why it is the body's thermal buffer — same joules, smaller temperature swing.
Latent heat (phase change)
Heat to melt or boil a mass m, with no temperature change while the phase changes.
In the exam: A heating curve's flat plateaus are the latent-heat regions — read them as 'energy in, temperature flat'.
Ideal gas law
Pressure × volume tracks amount of gas × absolute temperature.
In the exam: Most stems hold two variables fixed — the question is really 'which ratio survives?' (P₁V₁ = P₂V₂ at fixed n, T).
Combined gas law
For a fixed amount of gas, this ratio is conserved between any two states.
No-calculator habit: Gas-law temperatures must be absolute: add 273 to °C first. Doubling 27 °C does NOT double the pressure — 300 K to 600 K does.
Exponential decay & half-life
Half-life thinking covers radioactive decay and drug clearance alike: quantities that halve on a fixed clock. You almost never need the exponential formula itself — counting halvings is the exam-speed method.
Decay by half-lives
What remains after time t: the starting amount halved once per elapsed half-life.
In the exam: Work backwards too: if one-sixteenth remains, four half-lives have passed — no logarithms required.
Activity tracks amount
A sample's decay rate is proportional to how much undecayed material remains — so activity halves on the same clock.
No-calculator habit: Chain the halvings: after 3 half-lives, ½ × ½ × ½ = one-eighth remains. Ten half-lives ≈ one-thousandth (2¹⁰ = 1024) — a beautiful shortcut worth memorising.
Knowing the formula is the easy half
Section III rarely asks you to recite a relationship — it hands you an unfamiliar setup and asks what must follow. That skill comes from timed practice against exam-style stems, with an honest explanation for every answer. The free 6-question practice test is the fastest way in — Section III science at the real two-minute pace, no sign-up to start.
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