Pressure inside a liquid
Solids are not the only things that produce pressure. When a liquid is poured into a vessel, a pressure arises on that vessel because of the weight of the liquid.
When a solid object is placed on a table, a pressure arises on the table because the force due to the object's weight is spread over the region where object and table touch. It is exactly the same with a liquid — the force due to the liquid's weight is spread over the area of the base of the vessel.
Not only the base
Unlike a solid, a liquid also produces a pressure on the walls of the vessel holding it. Make a hole in the side of a tank and water squirts out of it — that is the evidence.
What else is special about liquid pressure
Besides pressing on the walls, liquid pressure has several other important features. Over the next few pages we shall settle each of them with an experiment:
- Does the pressure act in every direction?
- Is the pressure the same at the same level?
- What happens to the pressure as the depth increases?
- Does the shape of the liquid column affect the pressure?
Once we have answers to those four questions, we shall have a formula for the pressure at any depth.