Mass vs Compression: How Do They Exert Pressure?

[D9 XTC]

I'm curious about how mass and compression differ in how they exert pressure. For example:

You have a piece of wood. On the woods sits a 100lb weight. Somewhere else on the wood is a bolt going through it with a nut on the other side. This bolt and nut is tightened so that it exerts 100lbs of pressure just like the 100lb weight is doing.

Am I right to think that there are just multiple was of exerting pressure?

 

[S_Happens]

Weight is a Force, while pressure is Force per Area. This means that 100 lbs is not a pressure at all. The most common unit in the US would be lbs/in^2 (pounds per square inch) or psi (don't worry about psi, psia, or psig yet).

Ignoring how the force is applied (gravitation vs tensile load) all you need to do is compare the forces to the areas. Obviously for the bolt, the area is quite small. This means for an equivalent pressure to the one the 100 lb weight applies, there probably needs to be a smaller force.

Also ignoring where the forces are located on the piece of wood, you could for the most part consider these two pressure similar. If the piece of wood were supported directly underneath the weight, then the two cases would be similar enough to be considered equal for this simple question.