# engineering mechanics help

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#1
A steel wire 1m long has a mass of 2038.74kg hanging from it. Determine the diameter of the wire if the maximum lateral strain permissible is 0.102 and Poisson's ratio is 0.3. Take E as 30MPa. (Answer:50mm).

I seem to blank out when trying to find the same answer. Some help would be much appreciated!!
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1 year ago
#2
Poisson's ratio is (minus) lateral strain over longitudinal strain, rearrange this to give longitudinal strain.

Then E is stress/strain (the length does not matter since you have strain already), you have E and strain so rearrange to find the maximum stress. Then stress is equal to force/area, the force you have from the weight hanging in gravity. Then rearrange that to give the area and then that using circular area equation to give the diameter.

Also to make it easier to solve, a MPa is N/mm2 so you don't need to convert E really and simply put it in the rearrangement.
(Original post by ddsizebra)
A steel wire 1m long has a mass of 2038.74kg hanging from it. Determine the diameter of the wire if the maximum lateral strain permissible is 0.102 and Poisson's ratio is 0.3. Take E as 30MPa. (Answer:50mm).

I seem to blank out when trying to find the same answer. Some help would be much appreciated!!
1
#3
(Original post by Vikingninja)
Poisson's ratio is (minus) lateral strain over longitudinal strain, rearrange this to give longitudinal strain.

Then E is stress/strain (the length does not matter since you have strain already), you have E and strain so rearrange to find the maximum stress. Then stress is equal to force/area, the force you have from the weight hanging in gravity. Then rearrange that to give the area and then that using circular area equation to give the diameter.

Also to make it easier to solve, a MPa is N/mm2 so you don't need to convert E really and simply put it in the rearrangement.
Thankyou very much!! I got the answer! I kept using the wrong formula...
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