• defdek
In summary, the problem involves finding the stresses in two steel rods and a copper rod with a diameter of 20mm supporting a load of 20kN. The equations l=FL/AE and lE/L are used to calculate the stresses, with the values for E being 2.05 GN/m^2 for steel and 1.10 GN/m^2 for copper. The unit symbol for GN/m^2 is GPa. The relevant equations must be listed and solved using an equilibrium equation.
defdek
The original question:
2 steel rods and copper each of 20mm diameter together support a load of 20 kN. Find the stresses in the rod. Take E for steel and copper as 2.05 GN/m^2 and 1.10 GN/m^2.

l=FL/AE

for steel
l=(20kN)(2m)/(0.0003141x3)(2.05 GN/m^2)=0.021
stress= lE/L=(0.021m)(2.05 GN/m^2)/2m=21525000

and should i do the same for copper?

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defdek: Your answer is currently incorrect. What you typed would be three steel rods, which is not what the question says. You omitted the other relevant equations.

You must list the relevant equations yourself. The PF rules state we are not allowed to list relevant equations for you, nor tell you how to approach or solve your homework problem. We can only check your math, after you do all of the work to figure out how to approach the problem. Hint 1: Try an equilibrium equation.

By the way, the correct unit symbol for GN/m^2 is called GPa. Only write GPa; do not write its derivation each time. See the international standard for writing units (ISO 31-0).

nvn said:
defdek: Your answer is currently incorrect. What you typed would be three steel rods, which is not what the question says. You omitted the other relevant equations.

You must list the relevant equations yourself. The PF rules state we are not allowed to list relevant equations for you, nor tell you how to approach or solve your homework problem. We can only check your math, after you do all of the work to figure out how to approach the problem. Hint 1: Try an equilibrium equation.

By the way, the correct unit symbol for GN/m^2 is called GPa. Only write GPa; do not write its derivation each time. See the international standard for writing units (ISO 31-0).

I found it. thanks for the hint

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