Pressure and Depth
2 marks · EasyExplain why the area of the base does not change the pressure difference between two points at different depths in a liquid.
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The area cancels out in the calculation as pressure is force per unit area; for a column, both the weight and the area increase together, so pressure depends only on depth, density, and gravity, not area.
Must show: mention area cancels
Also accept: Area is not in the formula; the weight and area both scale so pressure formula doesn't depend on it
Common mistakes: Thinking wider tank creates more pressure
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Marking points
B1 · 1 mark · States or explains area cancels when calculating pressure difference.
B2 · 1 mark · Correctly links to formula for pressure difference (p = h × ρ × g), not mentioning area.
Worked solution
Area appears in both the force (weight) and in the calculation of pressure (force divided by area), so it cancels out. Thus, pressure depends only on depth, density, and g.