Pressure in Fluids Lab
Investigate how fluid pressure depends on depth and density using an interactive U-tube manometer. Select from six real fluids, adjust depth with a slider, and watch pressures update instantly across multiple unit systems.
Guided Experiment: Depth and Pressure
If you increase the depth in a fluid, how do you predict the pressure will change? Will the relationship be linear?
Write your hypothesis in the Lab Report panel, then click Next.
U-Tube Manometer
Controls
Pressure Readout
Formula Breakdown
Hydrostatic Pressure
ρ = density of Water = 1000 kg/m³
g = 9.81 m/s²
h = depth = 5.00 m
Substituted Values
Absolute Pressure
Pascal's Principle
Pressure applied to an enclosed fluid is transmitted equally in all directions.
Buoyant Force
An object immersed in a fluid experiences an upward force equal to the weight of fluid displaced.
Data Table
(0 rows)| # | Trial | Fluid | Density(kg/m³) | Depth(m) | Gauge P(Pa) | Abs P(kPa) |
|---|
Reference Guide
Hydrostatic Pressure
The pressure at a given depth in a static fluid depends only on the fluid's density, gravitational acceleration, and the depth.
- is fluid density (kg/m3)
- = 9.81 m/s2
- is depth below the surface (m)
Pressure is independent of the shape of the container. Only depth matters, not horizontal position.
Pascal's Principle
A pressure change applied to an enclosed, incompressible fluid is transmitted undiminished throughout the fluid in all directions.
This is the basis of hydraulic machines. A small force on a small piston can lift a large load when the output piston has a larger area.
Buoyancy (Archimedes' Principle)
An object submerged in a fluid experiences an upward buoyant force equal to the weight of the fluid it displaces.
- Object floats when
- Object sinks when
- Buoyant force does not depend on the object's material, only its volume
U-Tube Manometer
A U-shaped tube filled with a known fluid measures pressure by the height difference between the two arms.
- is the measured fluid's density
- is the manometer fluid's density
- Mercury manometers are compact because mercury is 13.6 times denser than water
Absolute vs Gauge Pressure
Absolute pressure is measured from a perfect vacuum. Gauge pressure is measured relative to atmospheric pressure.
- Standard atmosphere: 101 325 Pa = 1 atm = 760 mmHg
- Gauge pressure is zero at the surface
- Tire pressure gauges read gauge pressure, not absolute pressure
Pressure Unit Conversions
| Unit | = 1 Pa |
|---|---|
| Pascal (Pa) | 1 |
| Atmosphere (atm) | 9.869e-6 |
| Bar | 1e-5 |
| mmHg | 7.501e-3 |
| mH2O | 1.020e-4 |
| psi | 1.450e-4 |
