a steel wire length 4 metre and diameter 5 mm is stretched by 5 kg weigt to find the increasing its length the young modulus of Steel by 2.4 multiplied 10 dyne cm -2
Answers
Answer:
What force is required to stretch a steel wire of cross-section area 1 cm to double its length?
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Much as I dislike correcting other people - here it goes:
Assume that we actually have steel which can reach 100% elongation (it would have to very ductile and soft). Assume that there is no strain hardening. Assume that necking doesn’t occur. Assume that properties of steel remain the same during the whole process.
The cross-section of the steel wire with 1 cm2 will reduce to about 50% of the original - that is, it will be about 0.5 cm2 when the length is doubled.
Modulus of steel is about 200 GPa - BUT ONLY WITHIN LINEAR RANGE. So - the calculations involving modulus, strain etc. are simply wrong.
Typical strain-stress curve for ductile steel is shown below (there is some strain hardening evident, but let’s assume there is none): our steel would have to be softer, with maximum strength probably well below 200 MPa. Let’s assume Fmax =200 MPa…