Simple stress, strain, elongation relationship question

[Iclaudius]

Howdy ya'll,

a relatively simple question,

A circular bar 20mm in diameter and 1m long is subjected to an axial load of 50kN. Determine:

(i) The normal stress.
(ii) The normal strain.
(iii) The elongation.

Assume the material is steel with an Elastic Modulus of 200GPa.

ok so i got normal stress = 159 MPa, normal strain = 795*10^-6,
but here is my problem - solving for elongation why can i not just plug in the strain amount and solve for the change in length i.e strain * original length = change in length?
by the way elongation = 0.8mm which is not what i get using the aforementioned method.

(sorry for no math symbols)
Thanks in advance,
Claudius

 

[Mapes]

795 x 10^-6 multiplied by 1 m is not approximately 0.8 mm?

 

[Iclaudius]

oh snap, don't know what i was thinking lol, thanks for pointing out my oversight, guess i need more practice with the metric system :(