Physics · 1.8 Pressure · Paper 6 practical
Pressure in Liquids. Dive in.
Move a pressure probe through a liquid and see how pressure depends on depth and density. Verify p = hρg: pressure increases with depth, with density, and acts equally in all directions.
0625 Topic 1.8 — Pressure
p = hρg
Paper 6 — ATP
Drag the probe; or use the depth slider. Space record · R reset.
Variables
20.0
—
9.81
Live readouts
Depth h
0.20 m
Density ρ
1000 kg/m³
Pressure p = hρg
1962 Pa
Manometer height
20.0 cm
Pressure increases linearly with depth and acts equally in all directions at a point.
Trial data — p vs h
Move the probe to five depths and record the pressure.
p vs h — gradient = ρg
📋 Method (Cambridge ATP procedure)
- Connect a pressure probe (or a thistle funnel with rubber sheet) to a U-tube manometer.
- Lower the probe to a measured depth h in the liquid; record the manometer height difference (∝ pressure).
- Repeat at five depths; plot pressure against depth.
- Rotate the probe at one depth to show pressure is the same in all directions.
Analytical control: plot p against h. A straight line through the origin confirms p ∝ h; gradient = ρg.
⚠ Sources of error & precautions
- Measure depth to the centre of the probe, viewing perpendicular to the scale (parallax).
- Air bubbles in the tube give false manometer readings — remove them first.
- Keep the liquid temperature (and so density) constant.
🎯 Syllabus reference (0625)
- 1.8 Pressure — define pressure p = F/A; recall and use p = hρg for the pressure due to a liquid column; describe how pressure in a liquid increases with depth and acts equally in all directions.