5 · IGCSE Physics
Pressure in liquids
Change the depth of liquid and its density, move the pressure probe, and watch how jets from deeper holes leave faster and travel further.
p = ρ g h
Δp = ρ g Δh
jet speed v = √(2 g h)
g = 9.8 m s⁻²
Δp = ρ g Δh
jet speed v = √(2 g h)
g = 9.8 m s⁻²
Try this
- Set H = 1.00 m and compare the three jets: which hole is deepest, and how does its pressure compare with the shallowest hole?
- Double the probe depth from 0.300 m to 0.600 m and check that ρgh doubles exactly.
- Switch from oil to glycerol: the pressure at each hole rises, yet the jets land in the same places — use v = √(2gh) to explain why density cancels.
Common error: h in p = ρgh is the depth measured down from the liquid surface, not the height above the bottom of the container, and it must be in metres to give pascals.