Fluids
Pascal's principle
Equal pressure in a confined fluid: F₂/F₁ = A₂/A₁, so a larger piston gives a larger force.
Pascal's principle — interactive physics simulation. Press Play to inspect the two hydraulic pistons: equal pressure transmits force according to F₂/F₁ = A₂/A₁. Free browser-based virtual physics lab with live SI measurements and a guided tutorial.
Pascal's principle
Pressure applied to a confined fluid is transmitted undiminished; force scales with piston area.
In an ideal hydraulic system P = F/A is the same at equal depth, so F₂/F₁ = A₂/A₁. A larger output piston provides a larger force while moving a shorter distance.
- P transmitted equally
- F₂/F₁ = A₂/A₁ (hydraulic lift)
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 hydraulic lift has a small input piston and a much larger output piston, connected by a sealed fluid. If you push on the small piston, why does the large piston lift a much heavier load?
Predictions to weigh
- The output force equals the input force no matter the piston sizes.
- The output force is smaller because the fluid absorbs some of the push.
- The output force is multiplied in proportion to how much larger the output piston's area is.
Variable roles
What you set:
- Input piston area A₁ (m²)
- Output piston area A₂ (m²)
- Input force F₁ (N)
What you measure:
- Output force F₂ (N)
How the investigation runs
- Open the fluid-pascal preset and press Reset. Two connected pistons of different areas share a sealed, incompressible fluid.
- Enable the input/output pressure and force readouts.
- Set the input piston area, output piston area, and input force for each trial, and record the output-force reading.
What the printable worksheet asks students to work out
- For one trial, compute F₂ = F₁ · (A₂/A₁) and compare it to the reading.
- Pascal's principle says pressure applied to an enclosed fluid is transmitted equally everywhere. Use P = F/A on both pistons to explain why F₂/F₁ must equal A₂/A₁.
Where this shows up beyond the lab
- A car hydraulic jack uses a small hand-pump piston to lift an entire car. Using your data, explain roughly how much larger the jack's output piston area must be than its input piston area, relative to the force you can apply by hand and the car's weight.
- If the output piston lifts a load with 10× the input force, how far does the output piston move compared to how far you push the input piston? (Hint: think about conservation of fluid volume.)
- 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 Pascal
- Press Play
- Pressure transmits
- 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.