can somebody please help
Consider two straight bars of uniform cross section made of the same material. Bar 1 has an axial length of 1 m and a square cross section with side length 1 mm. Bar 2 has an axial length of 3 m and a round cross section with 2 mm diameter. When subjected to 1 KN axial tension, bar 1 elongates by 5 mm. What will be the elongation of bar 2, δ2, if it is compressed axially with a load of 25 KN?

Question

can somebody please help
Consider two straight bars of uniform cross section made of the same material. Bar 1 has an axial length of 1 m and a square cross section with side length 1 mm. Bar 2 has an axial length of 3 m and a round cross section with 2 mm diameter. When subjected to 1 KN axial tension, bar 1 elongates by 5 mm. What will be the elongation of bar 2, δ2, if it is compressed axially with a load of 25 KN?

anonymous · Answer

Bar 1 and 2 are made of the same material this indicates they have the same Young's Modulus of Elasticity E. By using the Equation 
|dw:1367402655844:dw|
where P is the axial(tensile or compressive) force acting, L is the original Axial Length, and A is the area of cross section. 
when we write this equation for both the bars, we can equate the R.H.S as the L.H.S is the same(E is the same as I explained earlier)
and we already know the value of elongation in bar 1, the equation will have only one unknown (the elongation of bar2)
|dw:1367402867282:dw|
Negative sign is because of the Compression. And final answer will also have negative sign, indicating compression. The second bar did not undergo Elongation, it underwent Compression coz of the Compressive Force.
I calculated the answer should be 0.11 m.