The BPhO Year 7/8 and Junior Physics Challenges don't test a hidden extra syllabus — they test how comfortable a child is with a set of everyday physics facts, applied to situations they haven't seen phrased quite that way before. Below is a plain-English tour of the ideas behind our BPhO challenge toolkit flashcard deck: twelve facts across forces, gravity, energy, electricity, sound and density. It's a companion to our full BPhO guide, not a repeat of it — that piece covers who runs the challenges and how to enter; this one is about the physics itself.

Forces: balanced, moving, and squeezed

A steady speed means the forces on something are balanced, not that nothing is acting on it. Picture a skydiver falling at a constant speed with the parachute open: the air resistance pushing up is exactly equal to their weight pulling down, so the resultant force is zero. Balanced forces don't mean "not moving" — they mean "not changing." Only an unbalanced force can speed something up, slow it down, or bend its path. So when a challenge question says "constant velocity," it's quietly telling you the forces cancel.

Speed is distance divided by time, which is why the unit comes out as metres per second. It's worth keeping a few real numbers in your head to sanity-check an answer: a brisk walk is about 1.5 m/s, a sprinter around 10 m/s, a car on the motorway roughly 30 m/s, and sound in air about 340 m/s. With a minute or so a question, that kind of quick estimate is what catches a slipped decimal point or a division done upside down.

Pressure is force divided by area, and its unit — the pascal — is one newton per square metre. Halve the area and you double the pressure, which is why a drawing pin goes in point-first and why snowshoes stop you sinking into snow: same force, spread differently.

Gravity: mass, weight, and the number 10

Mass and weight are not the same thing, even though people use the words interchangeably. Mass is the amount of matter something is made of, measured in kilograms, and it doesn't change no matter where you take it. Weight is the pull of gravity on that mass, measured in newtons, and it does change — take a 60 kg astronaut to the Moon and they're still 60 kg, but the pull on them drops from about 600 N to about 100 N, because the Moon's gravity is roughly a sixth of Earth's. Bathroom scales measure a push and label it in kilograms, which is a shortcut that only works while you're standing on Earth.

Weight equals mass multiplied by gravitational field strength, and on Earth that field strength is about 10 newtons per kilogram. The precise value is closer to 9.8 N/kg, but challenge questions nearly always let you round to 10. The habit worth building is writing the unit every time: 3 kg is a mass, 30 N is a force, and a bare "30" on its own is only half an answer.

Energy: stores that fill and empty

Energy is described in terms of stores and how it transfers between them, not created or destroyed. Lift a ball to the top of a slide and you fill its gravitational potential store; let it go and that energy transfers into the kinetic store as it speeds up, and into the thermal store of the slide and the air through friction. The total amount never changes — it just moves house. The other named stores worth having ready are elastic potential, chemical, thermal, magnetic, electrostatic and nuclear.

The prefix "kilo-" always means multiply by 1000, in any unit. A 2 kW kettle is rated at 2000 W, and because a watt is a joule every second, that kettle transfers 2000 J of energy for every second it's switched on. The same scaling rule applies everywhere — mega- is ×1,000,000, centi- is ÷100, milli- is ÷1000 — and converting everything to one unit before calculating is the step that saves the mark when a question mixes km, m and cm in the same sentence.

Electricity: what's measured, and how it's wired

An ammeter measures current and sits in series with a component; a voltmeter measures potential difference and sits in parallel across it. In a single-loop series circuit the current is identical at every point, so where in the loop you place the ammeter doesn't change the reading — it's the same everywhere.

A parallel circuit gives each branch its own path back to the cell, so a break in one branch doesn't stop the others. That's the whole reason a house doesn't go dark when one bulb blows: the lights are wired in parallel, not in series. Two identical bulbs in parallel are each just as bright as a single bulb on its own, because each gets the full supply voltage; wired in series, they share the voltage and both burn dimmer.

Sound: a vibration that needs company

Sound is a vibration carried from particle to particle, so it needs a medium — a solid, a liquid or a gas — and cannot cross empty space. Ring a bell inside a sealed jar and pump the air out, and the ringing disappears even though you can still see the hammer striking, because light needs no medium at all. That's why space is silent, and why sound actually travels faster through water, and faster still through steel, where the particles are packed together more tightly and pass the vibration on more quickly.

Sound travels through air at roughly 340 m/s, which is why counting the seconds between a lightning flash and its thunderclap tells you the distance. Light covers any distance on Earth close enough to instantly, so the flash arrives at once and the sound trails behind at about a third of a kilometre every second — divide the count by three for kilometres. The same fact runs echo questions, with one twist: an echo has made a round trip, so a clap that returns after 2 seconds has travelled to the wall and back, meaning the wall is about 340 m away, not 680 m.

Matter: what "denser" actually means

Density is mass divided by volume, and water — at 1 gram per cubic centimetre — is the yardstick everything else gets compared against. Wood, at roughly 0.7 g/cm³, floats; iron, at about 7.9 g/cm³, sinks. Size is a distraction here: a huge log floats and a tiny nail sinks, because what decides it is whether the object is more or less dense than the water it displaces, not how big or heavy it is in absolute terms.

Why knowing these cold is worth it

None of this replaces understanding the physics — every fact above comes with the reason it's true, because a fact half-remembered gets misapplied with confidence, which is worse than not knowing it at all. What fluency with these facts buys is time. On a paper of 25 or 30 questions in 25 minutes, a child who has to re-derive "weight equals mass times gravity" from scratch is spending seconds they don't have; a child who just knows it gets to spend that time on the question that actually needs working out.

If you'd like to see why some of these ideas trip children up specifically, common BPhO mistakes and misconceptions goes through the reverse side of this list. And if you're wondering whether any of this is "extra" physics your child hasn't met yet, how BPhO connects to the KS3 curriculum maps every one of these facts back to mainstream KS3 topics.

FAQ

Do I need to memorise all of these facts before sitting a BPhO challenge?

No. Think of this as a map of the ideas the questions draw on, not a checklist to tick off before the quiz. Both the Year 7/8 and Junior Physics Challenges are described by BPhO itself as a Quiz, not an exam — the best preparation is being comfortable with these facts, not having crammed them the night before.

Where do these facts come from?

From our own BPhO challenge toolkit flashcard deck at aitutors.me — twelve cards covering forces, gravity, energy, electricity, sound and density, written and checked in-house. BPhO doesn't publish past questions for these online quizzes, so nothing here is reproduced from any BPhO paper.

Why does the BPhO test everyday physics facts rather than advanced content?

Because both challenges are built for KS3 and Year 9-10 students and are explicitly low-stakes — the questions reward clear thinking about physics your child already meets in lessons, not memorised content beyond the syllabus.

Duke Harewood built aitutors.me's KS3 physics tutor, Professor Newton, around exactly this kind of everyday reasoning. This list grew out of the flashcard deck Professor Newton wrote for BPhO revision. Updated 26 August 2026.