When a tank contains water on top of mercury, the pressure varies with depth and depends on the density of each liquid.
Key concept:
Pressure in a liquid is given by:
P = ρgh
Where:
- ρ = density of the liquid
- g = acceleration due to gravity
- h = depth
Behavior of pressure in the tank:
- In the water layer:
- Pressure increases gradually with depth
- Rate of increase is lower because water has lower density
- At the interface of water and mercury:
- Pressure is continuous (same from both sides)
- In the mercury layer:
- Pressure increases more rapidly with depth
- Mercury is much denser than water, so pressure rises faster
Important points:
- Pressure depends on both depth and density
- Total pressure at the bottom = pressure due to water + pressure due to mercury
- Mercury contributes more to pressure because of its higher density