Stress on 25 micron Fiber Under Elongation Load

[benndamann33]

This doesn't seem particularly hard, thought it was simply an F/A situation but apparently not. A fiber with a diameter of 25 micro meters is subjected to elongation load of 25 g along the fiber axis. What is the stress on the fiber? Is the applied stress a shear or a tensiles stress. I said it was a tensil stress and went on to compute F/A. F was .025Kg * 9.8N and A was simply ((25*10^-6)/2)^2*pi. The resultant stress was 500 MPa. The correct answer is .125 MPa. Any suggestions??!

 

[berkeman]

I get the same answer as you. Maybe the text answer is wrong?

 

[benndamann33]

yeah I'm going with text is wrong, .125 is found by not dividing the radius by 2 and then dividing by a factor of 1000...haha only thing I could find out, but thank you!