- #1

problem:

I know that youngs modulus (E) is known as stiffness. but when solving for elongation you can write e=FL/AE as F=se where s=AE/L and s is also known as stiffness. so I'm confused why is s and E known as stiffness when E is in the definition of s. what exactly is the stiffens that s talks about and E talks about?

attempt at sol:

I see the units of s are N/m so i think that the interpretation for s is the same as for a spring constant ie. a certain amount of force will cause a certain displacement F/k=x. for E, i know that stress=strain*E, so that a certain stress will cause a certain strain ie. stress/E=strain.

conclusion:

so i think that the stiffness that E talks about is more like how difficult is it to strain by a certain percentage a certain object. as oppose the stiffness that s talks about is more of how difficult is it to move a point certain distance. but I'm still confused on how to interpret the units of E. I know that for k its N/m so i read it as "Newton for every meter" but for E its N/m^2 so i think its more like "Newton for every Area"? if so what area.

please correct me if I'm wrong thanks.