# Pressure Lab - Solid and Liquid Pressure, Pascal's Law, Air Pressure

> Middle-school pressure lab: bricks on a sponge, a U-tube gauge probe, vessel shapes, communicating vessels, ship lock, hydraulics, Torricelli and practice.

- URL: https://qilingtools.com/en/physics/pressure
- Category: Physics Tools (https://qilingtools.com/en/physics)
- Tags: [Physics](https://qilingtools.com/en/tags/physics), [Education](https://qilingtools.com/en/tags/education)
- Last updated: 2026-10-29
- Price: Free, no sign-up
- Privacy: Runs locally in the browser; files are never uploaded

A hands-on lab for the pressure chapter of middle-school physics. Put a brick flat, on edge or upright on a sponge and watch the dent, or drag a pressure probe through a tank and watch the U-tube gauge respond. Further pages cover vessel shapes, communicating vessels (teapot, boiler gauge, animated ship lock), the hydraulic press and Torricelli's tube, and a practice page drills p = F/S and p = ρgh.

## How to use

1. Pick a topic at the top: solids, liquids, vessel shape, communicating vessels, Pascal's law or air pressure
2. Move the sliders, or drag the probe or piston on the canvas, and watch the picture and numbers change
3. Read the worked calculation in the result card and the key points below it
4. Open Practice for random questions with instant marking and full solutions

## Features

- Brick orientations and vertical/horizontal cuts, with a sponge dent showing pressure
- Draggable U-tube gauge probe showing equal pressure in all directions at one depth
- Wide-top, straight and narrow-top vessels: force on the base vs weight of liquid, plus the flipped-vessel problem
- Communicating vessels you can pour into, a teapot, a boiler gauge and a step-by-step ship lock
- Hydraulic press F1/S1 = F2/S2 with work conserved; Torricelli tube with tilt, altitude and an air bubble
- Nine types of random practice questions (g = 10 N/kg) with instant marking and worked solutions

## FAQ

### What is h in p = ρgh?

It is depth: the vertical distance from the free surface of the liquid down to the point. If the water is 50 cm deep and the point is 10 cm above the bottom, its depth is 40 cm.

### Why is the force on the base not always the weight of the liquid?

The force on the base is F = pS = ρghS, which depends only on depth and base area. With straight walls F = G; with a wide top the walls hold up some liquid so F < G; with a narrow top the walls push down on it so F > G. Always find the pressure first.

### How do I find the pressure of the container on the table?

Treat it as a solid: the force is the total weight of container plus liquid, F = G(container) + G(liquid), then p = F/S with S the contact area on the table.

### Does tilting Torricelli's tube change the mercury height?

No. The vertical height stays about 760 mm at standard pressure; only the length of mercury along the tube grows. A wider tube or a deeper dip makes no difference either. Only a change in air pressure, or air getting into the tube, lowers the height.

### What value of g do the practice questions use?

They use g = 10 N/kg, as in Chinese middle-school exams. Type a number; forms like 1.2e3 or 1.2×10^3 also work. Answers within 2% of the exact value are marked correct.

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