Brainlag PlusPressure as force per area, p = F/A with areas in cm², pressure in a column of liquid p = hρg (Higher), upthrust and floating (Higher), and atmospheric pressure.
Force spread over an area
pressure = force normal to a surface ÷ area of that surface
p = F ÷ A
p in pascals (Pa), F in N, A in m². 1 Pa = 1 N/m². All three boards: recall.
A fluid (a liquid or a gas) presses at right angles (normal) to every surface it touches.
- A 60 kg dancer on one foot, area 150 cm², g = 9.8 N/kg
- F = 60 × 9.8 = 588 N
- A = 150 ÷ 10 000 = 0.015 m²
- p = 588 ÷ 0.015 = 39 200 Pa = 39.2 kPa
1 m² = 100 cm × 100 cm = 10 000 cm². Dividing cm² by 100 is the classic slip.
The rest of this lesson and its 9 practice questions are in Plus.
Screen 1 of 5, free to read.
- 9 exam-style questions, marked as you go, each with a worked solution
- Anything you get wrong is saved to your flashcards