Unit Sprint: Unit Conversion Game for GCSE Physics

How to play Unit Sprint

Unit Sprint is a unit conversion game for GCSE physics. Each question shows a value with a unit, such as 45 km, and the unit to change it into. You pick the right answer from four choices.

You have 60 seconds. Each right answer scores a point. From the second right answer in a row, each one scores an extra point, so a long streak doubles your points. A wrong answer ends the streak.

The questions get harder as your score climbs. You start with prefixes such as kilo, centi and milli. At 5 points the game moves on to minutes, hours, km/h, kilowatt-hours and tiny prefixes such as micro and nano. At 12 points you reach areas, volumes and answers in standard form. Tick the harder start to skip the first stage.

If you get one wrong, the game shows the working: the factor, and whether to multiply or divide by it. The clock keeps running while you read it, so press Next as soon as you are ready.

The practice switch turns the clock off. You then get a round of exactly ten questions, with your score at the end.

The science behind unit conversions

Physics equations work in SI units. Distance goes in metres, mass in kilograms, time in seconds, energy in joules and current in amps. Exam questions often give values in other units, so you convert them first and then use the equation.

A prefix is a short way to write a power of ten. Kilo (k) means 1,000, or 10³, and mega (M) means 10⁶. Centi (c) is 10⁻², milli (m) is 10⁻³, micro (μ) is 10⁻⁶ and nano (n) is 10⁻⁹. To turn 3.2 kJ into joules, multiply by 1,000 to get 3,200 J. To turn 45 mA into amps, divide by 1,000 to get 0.045 A.

Time units use 60 instead of powers of ten. A minute is 60 seconds and an hour is 3,600 seconds, because you multiply by 60 twice. For speed, 1 m/s is the same as 3.6 km/h, so you divide by 3.6 to go from km/h to m/s. A car at 54 km/h is moving at 15 m/s. A kilowatt-hour is the energy a 1 kW device transfers in one hour, which is 1,000 W × 3,600 s = 3,600,000 J.

Areas and volumes catch many students out. A square with 1 cm sides has an area of 1 cm². Each side is 0.01 m long, so the area is 0.01 × 0.01 = 0.0001 m², or 10⁻⁴ m². The game offers 10⁻², the factor for a length, as a wrong answer because so many people use it. For a volume you cube the factor, so 1 cm³ is 10⁻⁶ m³.

Every GCSE physics course expects these skills. AQA (8463) lists SI units and prefixes from tera to nano as working scientifically skills WS 4.3 and WS 4.4. Edexcel (1PH0) covers them at the start of its course, in Topic 1, which includes changing hours into seconds. OCR Gateway (J249) lists them as WS1.4c and WS1.4d. OCR Twenty First Century (J259) asks students to convert between m/s and km/h, and it uses kilowatt-hours in the energy transferred equation, E = P t.

In the exam you get a sheet with the physics equations on it. It gives you the equation but leaves the unit changes to you. You can see each board's sheet on our physics equation sheet page.

Tips for faster unit conversions

• Ask yourself whether the new unit is bigger or smaller. Going to a smaller unit, such as km to m, gives a bigger number.
• Count the powers of ten between the two prefixes. Kilo to mega is a jump of 10³, so 5,200 kJ is 5.2 MJ.
• For km/h to m/s, divide by 3.6. For m/s to km/h, multiply by 3.6.
• For hours to seconds, multiply by 3,600. Multiplying by 60 only gets you to minutes.
• Square the length factor for an area and cube it for a volume.

A streak doubles the points for each answer, so a careful run of right answers usually beats a rushed one with gaps in it.

Use Unit Sprint in the classroom

Unit Sprint suits Years 9 to 11 and fits into the first few minutes of a lesson. One sprint lasts a minute, so a class can play three rounds and compare scores inside a single starter.

Before a calculation lesson, run a sprint on the board. Ask students to call out whether to multiply or divide before anyone taps an answer. The wrong options come from real errors, such as going the wrong way, using the wrong power of ten or using the length factor for an area. Ask the class which error each wrong option shows.

For students who freeze under a clock, the practice switch gives a calm round of ten questions with no time limit. Stronger students can tick the harder start and begin with hours, km/h and nano prefixes.

Pair it with Equation Rearranger, where some values come with prefixes that students convert before they calculate. There is no sign-up, and the game runs in the browser on phones, tablets and Chromebooks. The teachers page has more ways to use the games in lessons.

Questions people ask

Here are answers to common questions about converting units in GCSE physics.