give 10 differences between solid pressure and liquid pressure
Answers
First off, they are both force divided by area. Pounds per square inch. Newtons per meter squared. That sort of thing.
Pressure is often used with fluids (gases or liquids), whereas stress is more often used with solids.
One major difference is that pressure only acts perpendicular to a surface, whereas stress can also be parallel to a surface as well as perpendicular to it. A stress parallel to a surface is called shear stress. The perpendicular part is called normal stress.
Pressure can only be positive wheres normal stress can be negative or positive. A negative normal stress is called tension. A positive normal stress is called compression, or compressive stress. Come to think of it, sometimes the sign convention is the other way around, with tension being positive and compression being negative. For some reason, structural analysts seem to do it that way. And they should be the experts, eh? But I always think of compression as being positive.
If you want to get fussy and mathematical, stress is a tensor of order 2. Or is it rank 2? Something like that. Pressure is usually considered a scalar. Or sometimes people think of it as a tensor too, but with the diagonal entries all equal to p and the off-diagonal terms equal to 0. So then it's basically a stress tensor with constraints.
I don't know where all this internal external mumbo jumbo came from. This is mentioned a lot in the answers to the other thread that someone mentioned.
What is the difference between pressure and stress as they have the same units?
Several people there are saying that pressure is applied to the outside of things and that causes stress on the inside. Well, that's rot. Nice and simplistic sounding and they all jumped on the bandwagon, I guess. Pressure exists in the interior of fluids just the same as stress in solids. You can have stress in fluids too, by the way. It's just that shear stress in fluids requires continuous shearing motion (and viscosity) in the fluid whereas solids can sustain the stress continuously without moving. But inside the water in a swimming pool, there is pressure. You can feel it pressing on your ear drums when you dive down. But just becuase it's pressing in on the outside doesn't mean it is only on the outside. The pressure continues all the way to the inside of your body too. Sure, you could call that stress too if you like, but it's still pressure. You can also have stress on the exterior of a solid as well as inside. It's just the force applied at the surface divided by the area that it's applied to.