Question

A physics question that I am stuck on:

"Calculate the following, the diameter of a steel wire that has to hold a chandelier frame weighing 60kg. The material's yield resistance is ReL = 180 N/mm^2. The factor of security is 3."

Answer 1

Well, we have the weight of the chandelier frame at 60 kg, so we could convert that into Newtons
And then, the resistance is a measure of Newtons per mm^2, so it seems like we could find the area of the material we'd need; from there, if we assume the shape of the wire is a cylinder, finding the diameter from the area wouldn't be hard.
I'm not sure what "factor of security" refers to, so like before, I think there's probably something to the problem I'm missing

Answer 2

What I think my professor meant is the Security factor

Answer 3

or safety factor, he is unclear most times

Answer 4

Oh ok! I didn't know the term, but when I looked it up I got "safety factor (SF), expresses how much stronger a system is than it needs to be for an intended load"
So, I guess we can solve the problem for a chandelier that is 3 times as heavy as the one we are given. Since the intended load is 60 kg and the security factor is 3, we can solve the problem for a weight of 180 kg instead.

Answer 5

And that actually works out nicely for the numbers too.
180 kg is about 9.8*180 N, and the wire can support 180 N per mm^2. So, that means the wire would need to be 9.8 mm^2 in area to support the mass.
The diameter of that area would be \[2*\sqrt{9.8/\pi} \] which give us about 3.5 mm. So, I think that would be the diameter we need?

Answer 6

I think that sound plausible, you used the definition to indicate what area was required and subsequently, calculate the diameter!