Investigating Pressure Using Fizzy Drinks Bottles and Water

Understanding pressure is key to both physics and everyday life — from hydraulics and weather systems to the way submarines, pumps, and aircraft work. With a few empty fizzy drinks bottles and some water, students can explore how pressure changes with depth and how fluids behave under force, all with simple, recycled materials.

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The Experiment

Equipment:

• 1 L or 2 L clear plastic fizzy drinks bottles

• Water

• Nail or small pin

• Blu-Tack or waterproof tape

• Measuring cylinder or ruler

Method:

1. Fill the bottle with water and seal the top with the lid.

2. Use a pin to make small holes at different heights along the side of the bottle — near the top, middle, and bottom.

3. Cover the holes with Blu-Tack until you’re ready to test.

4. Remove the lid, then release the Blu-Tack and observe the jets of water emerging from the holes.

Students will see that the lower holes produce stronger, faster jets — showing that pressure increases with depth.

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The Science

The deeper the point in a liquid, the greater the pressure due to the weight of the water above it:

$$P = \rho g h$$

where:

• $P$ = pressure (Pa)

• $\rho$ = density of the liquid (kg/m³)

• $g$ = acceleration due to gravity (9.8 m/s²)

• $h$ = depth (m)

The jets from the lower holes travel further because the pressure — and therefore the force on the water — is greater. This same principle applies to dams, deep-sea diving, and how submarines must be engineered to withstand immense forces.

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Extensions

• Quantify the results by measuring how far each jet travels horizontally.

• Compare liquids (e.g. salt water vs fresh water) to see the effect of density.

• Discuss real-world examples such as hydraulics, atmospheric pressure, and Pascal’s Principle.

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Skills Highlight

• Designing and conducting a fair experiment using recycled materials

• Measuring and comparing qualitative pressure effects

• Linking observed patterns to mathematical relationships

• Understanding applications of pressure in science and engineering

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Why It Works in Teaching

This experiment is safe, inexpensive, and visually dramatic. Students can see immediately how depth affects pressure, reinforcing theoretical formulas with real, observable data — and all from an everyday object they recognise.