# Calculate the size of the cross section relating to tension

1. Jan 25, 2012

### joe465

1. The problem statement, all variables and given/known data

A medium carbon annealed steel rod has a rectangular cross section and must cope with a tension of 3 tonnes. The thickness of the rod is 15mm. Calculate the size of the cross section.

Tension limit = 3 tonnes
Thickness = 15mm
Cross Section = ????

2. Relevant equations

o = P/A or P = Ao

P = total external force in newtons
A = area of cross section in square millimetres
o = stress in newtons per square millimetre

3. The attempt at a solution

I do not have clue where to start since i'm given a tension limit in tonnes. Tension is when two forces act in opposite directions causing the body to elongate. Now if i presumed that the tension needed to act directly downwards then it would be right to assume:

3000 * 9.81 = 29430N

Now im stuck, am i on the right track?

Any help would be greatly appreciated

Thanks, Joe

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