# Aerospace Finding second moment of area using Euler's theory?

1. May 24, 2012

### dave.hills

Hi, I have just started a HND in Aeronautical Engineering and its been awhile since I have done any maths, need help with finding the second moment of area using Euler's theory!

I have Euler's equation : Force (P)= (pi squared (pi2)) * (modulus of elasticity (E)) * (second moment of area (I)) / (effective length squared (L2))

I then got I = P*L2/pi2*E (is that correct?)

P = 170KN - factor safety of 3 needed - 510KN
L = 8m
E = 200 GPa

I am struggling with the units, I need I in cm4 and can't work it out!

Thanks

2. May 29, 2012

### wsaleem

solve it for m^4 by taking P=170*1000N; L=8m, E=200*10^9Pa. You will get ur answer in m^4. Convert it into cm^4 by dividing it by 100^4. Also check the question carefully to make sure ure using the correct formula for I as it is different for different euler conditions which u'll find in ur text book or lecture notes.

3. May 29, 2012

### wsaleem

sorry my bad make the conversion by multiplying by 10^4 instead of dividing