Calculating Temperature Change for Steel Rod Stretching

[parttime]

a steel rod undergoes a streching force of 500n its crossectional area is 2cm^2 find the temp change that would elongate the rod by same amount
i useyoungs modulus to get change in length so ym= (F/A)/(deltaX/h)
so i solve for r (which is = to h from area of circle) and with a ym for steel of 20*10^10 i get delta X now i plug that into equation for linear
which is deltaX = (average coeffiecent of linear expation for steel) = 11*10^-6 Linitial(which is what is giving me problems) *delta T (temp)
i am not given the initial length how am i supposed to come up with it or substitute it for some other value??

 

[Andrew Mason]

i useyoungs modulus to get change in length so ym= (F/A)/(deltaX/h)
so i solve for r (which is = to h from area of circle)

What is r? h should be the length of the rod. When you do the thermal expansion, the length drops out.

AM