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 practice bank is free to start, and the free diagnostic shows where each section stands.
Get the dates that matter
Test-week checklists, registration deadlines and results day for the current GAMSAT cycle — nothing else.