Fluids
U-tube manometer
Applied P₁ > P₂ holds the left liquid surface lower; ΔP = P₁ − P₂ = ρgΔh.
U-tube manometer — interactive physics simulation. Applied P₁ > P₂ holds the left liquid surface lower; ΔP = P₁ − P₂ = ρgΔh. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Hydrostatic pressure
A U-tube manometer shows how pressure differences create height differences in a connected fluid.
Applied P₁ > P₂ holds the left liquid surface lower; ΔP = P₁ − P₂ = ρgΔh.
- P = ρgh
- ΔP = ρgΔh
Investigation brief
Plan the question before you open the lab
The brief mirrors the prerendered page: driving question, competing predictions, variable roles, governing laws, setup, analysis and extension prompts remain visible and in this order.
Driving question
A U-shaped tube holds water at different heights on each side, open to the air on both ends. What determines the pressure difference between the two columns?
Predictions to weigh
- The pressure difference depends on the total amount of water in the tube.
- There is no pressure difference as long as both sides are open to the air.
- The pressure difference depends only on the height difference between the two sides.
Variable roles
What you set:
- Left height h_L (m)
- Right height h_R (m)
What you measure:
- Pressure difference ΔP (Pa)
How the investigation runs
- Open the fluid-utube preset and press Reset. Water sits at different levels on the left and right sides of the U-tube.
- Enable the pressure-difference readout.
- Set the left and right water heights for each trial and record the pressure-difference reading.
Governing equation
Hydrostatic Pressure — P = ρ·g·h
Pressure in a fluid increases linearly with depth: P = ρgh. In a U-tube open to the air on both ends, the pressure difference between the two columns comes entirely from their height difference.
What the printable worksheet asks students to work out
- For one trial, compute ΔP = ρg(h_R − h_L) using water density 1000 kg/m³ and g = 9.8 m/s², and compare it to the reading.
- Your three trials use different absolute heights but the same pattern. Explain why ΔP depends only on the height difference, not on how full the tube is overall.
Where this shows up beyond the lab
- A mercury barometer uses the same principle but with mercury (density 13,600 kg/m³) instead of water. For the same height difference, would the pressure difference be larger or smaller than with water? By roughly what factor?
- Divers feel pressure increase the deeper they go. Use ΔP = ρgΔh to explain why the pressure at 10 m underwater is roughly double the pressure at 5 m.
- AP Physics 1 — Unit 8: Fluids
- General High School Physics — Fluids & pressure
- NGSS High School Physics — Forces and Newton's second law
- Welcome to Fluid Utube
- Press Play
- Read the height difference
- Open the Properties panel
- You did it!
Open the interactive simulation to build the scene, press Play, and explore with live measurements and a guided tutorial.