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Grade 8 Intermediate About 15 min Version 1 Awaiting review Premium

Pressure: force and contact area

Pressure tells us how concentrated a force is: pressure = force ÷ area. It is measured in pascals (Pa); 1 Pa is a force of 1 N spread over 1 m². The same brick presses harder on the ground when it stands on its small end than when it lies flat, because its weight is spread over a smaller area. That is why knives are sharp, nails are pointed, and tractors and snowshoes have wide bases.

What you will learn

  • Calculate pressure using pressure = force ÷ area.
  • Show that a smaller contact area gives a greater pressure.
  • Explain everyday examples of high and low pressure.

Before you start

  • Know that weight is a force measured in newtons.
  • Calculate the area of a rectangle.

Materials

  • Bricks measuring 20 cm × 10 cm × 5 cm (25 N each)
  • A thick foam block or a tray of damp sand

Equipment

  • Ruler to measure the dent

Procedure

  1. Stand one brick on its flat side, its long side and its end, recording each time.
  2. Stack a second brick on top and record again.
  3. Compare how deep the foam is pressed in.

How this simulation is simplified

  • Each brick weighs 25 N.
  • The foam is pressed in 1 mm for every 500 Pa.