# Engineering maths helpWatch

This discussion is closed.
#1
Hey, i am studying for my engineering materials exam, first year undergrad.

What is the minimal diameter of a copper wire that can support the mass of 100 kg without breaking?
The Young’ modulus of copper is 120 GPa, yield strength 190 MPa
and tensile strength 250 MPa.

I know to find the maximum diameter i have to use the tensile strength although using stress=force/area and i need to find diameter i'm not actually given force and need to find area which cant be found from the yield stress because i imagine the diameter for yield stress will be different than for tensile stress. Any help would be great, thanks !!
0
4 years ago
#2
(Original post by Engclasshelp)
Hey, i am studying for my engineering materials exam, first year undergrad.

What is the minimal diameter of a copper wire that can support the mass of 100 kg without breaking?
The Young’ modulus of copper is 120 GPa, yield strength 190 MPa
and tensile strength 250 MPa.

I know to find the maximum diameter i have to use the tensile strength although using stress=force/area and i need to find diameter i'm not actually given force and need to find area which cant be found from the yield stress because i imagine the diameter for yield stress will be different than for tensile stress. Any help would be great, thanks !!
engineering forum if there is such place must be better
0
4 years ago
#3
first find the weight on the copper wire using f=ma.

you know that stress = force / area, i.e.

rearrange to find the area:

substitute in what you know:

area of a circle is:

rearrange to find the diameter:

and so

i'm just guessing so i might be wrong.
0
#4
(Original post by samsama)
first find the weight on the copper wire using f=ma.

you know that stress = force / area, i.e.

rearrange to find the area:

substitute in what you know:

area of a circle is:

rearrange to find the diameter:

and so

i'm just guessing so i might be wrong.
Thanks so much!!
0
4 years ago
#5
(Original post by Engclasshelp)
Hey, i am studying for my engineering materials exam, first year undergrad.

What is the minimal diameter of a copper wire that can support the mass of 100 kg without breaking?
The Young’ modulus of copper is 120 GPa, yield strength 190 MPa
and tensile strength 250 MPa.

I know to find the maximum diameter i have to use the tensile strength although using stress=force/area and i need to find diameter i'm not actually given force and need to find area which cant be found from the yield stress because i imagine the diameter for yield stress will be different than for tensile stress. Any help would be great, thanks !!
Moved to Engineering forum
0
2 years ago
#6
thx but your second to the last step, your rearranging is wrong
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