- #1
cjm181
- 69
- 1
Homework Statement
This is the problem I am working through. I am up to (b). I am struggling with the units.
https://www.flickr.com/photos/93763273@N05/8815418518/lightbox/
My question is, why is the final answer in N/m^2? and why does the workbooks list stress in the units of N/m^-2
the beam is 100mm wide and 200mm deep
Homework Equations
m/I=σ/y
σ=(my)/I
I = (bd^3)/12
The Attempt at a Solution
I have drawn out the bending moment diagram, and calculated a max bending moment to be m = 8.333kN. This is the same as other people attempting this question are getting. So I am happy with that.
y = 100mm or 0.1m
I = (0.1x0.2^3)/12 = 6.66667x10^-5m^4
so, σ=(my)/I
σ=(8333 x 0.1) / 6.66667x10^-5
σ=12499499.94 N/m^2 or 12.5x10^6N/m^2
or
σ= 12.5 MN/m^2 or 12.5 N/mm^2
Thanks,
Craig