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Science

Pressure

Overview

Students investigate how pressure depends on both force and area, discovering why the same force can have very different effects depending on how it is applied.

Learning Objective
Students understand the concept of pressure as force per unit area and can apply this to explain real-world phenomena.

Resources needed

  • A flat board
  • A nail or sharp stick
  • A plastic bag filled with water or sand

Lesson stages

0 / 7 done
  1. 1 Press a flat hand onto a soft surface — the surface compresses a little.
  2. 2 Now press one finger on the same surface with the same force — it sinks further. Ask: what changed?
  3. 3 Introduce pressure: pressure = force divided by area. Same force on smaller area = higher pressure.
  4. 4 Ask: why are knife edges sharp? (Small area, high pressure with little force).
  5. 5 Ask: why do camels have wide flat feet? (Large area, lower pressure — do not sink into sand).
  6. 6 Ask: why does a person sink into snow but snowshoes prevent this? (Larger area, lower pressure).
  7. 7 Calculate: if a force of 10 N acts on an area of 2 m squared, what is the pressure? (5 Pa).

Tap a step to mark it as done.

Variations

  • Lie on a bed of nails — with many nails, pressure at each point is low enough to be safe.
  • Test pressure in liquids: measure water pressure at different depths using a bag with a small hole.
  • Discuss atmospheric pressure: why does it decrease with altitude?
More information

Teach: pressure, force, area, pascal, distribute, concentrate. The equation pressure = force/area is the most important formula at this level.

Focus on the qualitative concept — more area, less pressure — before introducing the formula and calculation.

Can students explain why snowshoes prevent sinking using the concept of pressure? Can they use the formula pressure = force/area to perform a simple calculation?

Press a nail point versus a flat board into sand or soil to demonstrate pressure differences.

Students often think larger force always means greater damage. A large force spread over a large area may cause less damage than a small force concentrated on a tiny area.

Pressure explains engineering design, atmospheric science, and biology (blood pressure).

Activity details
Secondary Medium 25 minutes 5 minutes prep Small Group, Whole Class Indoor & Outdoor
Topics
Pressure Force Physics