How to play Pressure Dive
Pressure Dive is a game for GCSE pressure calculations, and it has two scenes. In the first, four objects press on a surface: a stiletto heel, a snowshoe, a drawing pin and a tractor tyre. Each one has a force in newtons and an area, some in cm² and some in m². In the second scene, a diver goes down through the water and a depth gauge shows how deep they are.
Early questions ask you to find the pressure under one object, or to decide which of two objects puts more pressure on the surface. Later questions move to the diver. You find the pressure from the water at the diver's depth, or you pick the reason the pressure goes up as the diver goes deeper.
A round has ten questions, and diver questions can only come up in the last three. They use p = h ρ g, which is Higher tier. Each right answer scores 10 points, or 15 if you are quick. With the harder start, the diver can appear from question 4 onwards. After every answer, the game shows the equation, the values and the right result.
The science behind pressure in solids and liquids
Pressure tells you how concentrated a force is. The equation is p = F ÷ A, with pressure in pascals (Pa), force in newtons and area in square metres. One pascal is a force of one newton on each square metre.
A drawing pin has a tiny point, so a small push makes a huge pressure and the pin goes into the board. A snowshoe spreads your weight over a big area, so the pressure is low and you stay on top of the snow. A tractor tyre is wide for the same reason.
Areas in cm² catch a lot of people out. There are 100 cm in a metre, so 1 m² is 100 × 100 = 10,000 cm². To change cm² into m², divide by 10,000. A stiletto heel pressing down with 500 N on 2 cm² has an area of 0.0002 m², so p = 500 ÷ 0.0002 = 2,500,000 Pa. Dividing by 100 instead gives 25,000 Pa, which is 100 times too small. The page on the pressure equation has more on rearranging it.
In a liquid, pressure grows with depth because there is more liquid above pushing down. For a column of liquid, p = h ρ g. Here h is the depth in metres, ρ is the density in kg/m³ and g is the gravitational field strength in N/kg. At 2 m down in fresh water, p = 2 × 1,000 × 9.8 = 19,600 Pa. Sea water is denser, at 1,030 kg/m³, so the pressure at the same depth is a little higher. This is the pressure from the water alone, and the air above the surface adds atmospheric pressure on top. There is more on this on our pressure in liquids page.
Pressure in fluids is physics only in AQA GCSE Physics (8463, section 4.5.5), Edexcel GCSE Physics (1PH0, 15.7P to 15.17P) and OCR Gateway Physics A (J249, P1.3f to P1.3j), so it is not part of AQA or Edexcel combined science. The liquid equation is Higher tier on all three: AQA 4.5.5.1.2, Edexcel 15.14P and OCR P1.3j. AQA and OCR Gateway print it as p = h ρ g, and Edexcel prints P = h × ρ × g.
AQA says the value of g will always be given in a calculation. OCR's specification gives g near the Earth's surface as 10 N/kg. This game uses 9.8 N/kg and shows it on screen. Both pressure equations are printed on each board's exam sheet, so the practice that counts is the unit work.
Tips for pressure calculations
- Before you divide, change cm² into m² by dividing by 10,000.
- Pressure is force divided by area. Force times area is one of the wrong options.
- For the same force, a smaller area gives a bigger pressure. Use that to check your answer.
- For the diver, put the depth in metres: 250 cm is 2.5 m.
- Keep g in the liquid equation. Leaving it out makes the answer about ten times too small.
When you compare two objects, work out both pressures in pascals first. The object with the smaller force can still give the bigger pressure if its area is tiny.
Use this in the classroom
Pressure Dive suits Years 9 to 11. The object questions work for everyone on a GCSE Physics course, and the diver questions give Higher tier students in Years 10 and 11 practice with p = h ρ g.
The objects scene makes a good way into the topic. Ask why a drawing pin needs a sharp point while a snowshoe needs to be wide, then show a compare question and take a class vote before anyone calculates. After a lesson on floating and upthrust, use the harder start so students reach the diver questions quickly.
Practice mode takes the timer away for students who need longer. It needs no login, and the list of what we collect sets out what the site stores. The page for teachers has more classroom ideas.
Similar games
Moments are another forces topic that only GCSE Physics covers. In Moments Balance you balance a beam on a pivot. Our sister site has Density Mass Volume if you want more practice with density, and the all games page has the full list.
Questions people ask
Students and teachers often ask these questions about pressure.
How do you convert cm² to m² for pressure questions?
Divide by 10,000, because 1 m² is 100 cm by 100 cm. So 25 cm² is 0.0025 m². Dividing by 100 is the most common mistake.
Why does water pressure increase with depth?
The deeper you go, the more water there is above you. The weight of that water pushes down on every square metre below it, so the pressure rises. A denser liquid gives a bigger pressure at the same depth.
Is p = h ρ g on the GCSE equation sheet?
Yes, for GCSE Physics with AQA, Edexcel and OCR Gateway. It is a Higher tier equation. AQA and Edexcel combined science leave it out.
What is the unit of pressure?
The pascal, Pa. One pascal is a force of 1 N on an area of 1 m². Everyday pressures are often thousands of pascals, so you will also see kPa, where 1 kPa is 1,000 Pa.