I have the modulus of elasticity = 140MN^-2 and I came to 140x10^6 is this the problem? sorry not modulus of elasticity I meant yield stress. Anyway very confused now.....
Suppose the column is 2mm high. You will never buckle it no matter how much force you apply, just like you could never buckle a penny no matter how much force you apply. How much force could you apply before “mushing” it: F=AxYS.
OK, now suppose you tried to apply the same force, F=AxYS, to the same column that was 100meters high? You would buckle way before you ever got there.
So at what point do you switch from crushing to buckling? Substitute F=AxYS in the buckling formula to get the length at which this happens.
If you understand that, getting the right answer is just a matter of some algebra and using the right units.
If I were a teacher and a student got the right answer with no explanation, I would give him 0/10. If he had the right method showing how he got it but the wrong answer, I would give him 10/10- no, 11/10 for not wasting his time on the algebra.
OK, yes, not knowing if you got the right answer can be frustrating, but only if you are not sure you are going about it right.
I want to do it right and show all my working but the explanations aren't making much sense and have never came across F=AxYs so don't know what it all stands for and all the components of it are. Just really wish I could see it in practice for the equation then follow it.........
I gave you the formula to use back in post #13 of this thread. You tried to use that formula but made the mistake of plugging in yield stress instead of area moment of inertia for the 'I' term. Remember you have already calculated in post #6. Use that value in the formula for the 'I' term and you should get the right answer.
Simply having the formula doesn't do it. You have to understand that you have to substitue F=AxYS in the formula for Fcr and solve for l. Why is that a problem? The actual solving is just algebra, if you use consistent units, say N and m.
Just saw your post. What did you do and why? Saying you got some number is meaningless