How does pressure work?


Say something has 17 psi, why does it not then weigh an additional 17 pounds for every square inch? If there is that much air or water in there it has to start gaining weight at some point and I don’t understand why we can’t say something else if it doesn’t mean that.

In: Physics

PSI is pounds per square inch. It’s not a measurement of gravity on an object but the outward force of a gas or liquid. So 17 PSI means that each square inch has the equivalent of 17lbs pushing out on it in all directions of the container. So that is 17lbs going down as well as up so it counteracts each other as long as the container can’t expand one way vs the other.

One key thing to know is the difference between pound force and pound mass.

The pounds in psi is a force applied over an area of one square inch.

Pound mass is the measurement of force on an object due to gravity.