# Compression of an object and its length.

I have heard a claim that looks a little odd to me and Im hoping that someone can help.
In the gym there are foam rollers people use, some of them are 36 inches long and some are 16 inches. The claim is that the shorter ones can withstand greater weight than longer ones and will have less tendency to become deformed than the longer ones. If i recall the stress on an object is the force divided by the area, so if anything a smaller roller should do worse not better but intuitively i feel it shouldn't make any difference , the section of the roller the person is applying pressure to is basically the same.
Can anyone help in sorting this matter out.

phinds
Gold Member
I have heard a claim that looks a little odd to me and Im hoping that someone can help.
In the gym there are foam rollers people use, some of them are 36 inches long and some are 16 inches. The claim is that the shorter ones can withstand greater weight than longer ones and will have less tendency to become deformed than the longer ones. If i recall the stress on an object is the force divided by the area, so if anything a smaller roller should do worse not better but intuitively i feel it shouldn't make any difference , the section of the roller the person is applying pressure to is basically the same.
Can anyone help in sorting this matter out.
I agree w/ your analysis. The idea that a larger surface spreads out an applied force only applies to rigid surfaces and that's not the case for gym mats. Don't see why an extra mile or two of material off to the side would make the slightest difference to the part that pressure is applied to in this case. This assume, of course, that they are made of exactly the same material.

windy miller and CWatters