A stairwell is supported by two circular steel rods at one end. The other end supported above. The two steel rods are subjected to a total load of 12,800lbs. The rods are 24 ft long and E=30*10^6 psi. Select the rod based on the following specs. The rod deformation should not exceed 0.375 inches and the allowable tensile stress is 10,844 psi?

This seems to be more a "strength of materials" or civil/mechanical engineering design question than a physics problem.

Assume each rod gets half the load, or 6400 lb. Calculate the minimum circular area required to satisfy both the stress and the deflection requirements. From an available stock catalog for mild steel, pick the smallest diameter that satisfies both requirements.

I calculated reqd A got 32.8 psi to get diameter of 6.46 in/in. Am I going right way or did I miss something?

You missed something. 32.8 psi is hardly any stress at all.

To select the appropriate rod based on the given specifications, we need to calculate the maximum load that the selected rod can withstand without exceeding the allowable tensile stress, as well as the deformation caused by that load.

First, let's calculate the cross-sectional area of the rod. Since the rod is circular, the cross-sectional area is given by the formula:

A = π * (r^2)

Where A is the cross-sectional area and r is the radius of the rod.

To find the radius of the rod, we need to divide the diameter by 2. The diameter of the rod can be obtained by dividing the length of the rod by π:

d = 24 ft / π

Once we have the diameter, we can calculate the radius:

r = d / 2

Next, we need to calculate the maximum load that the rod can withstand. We can use the formula:

Load = Stress * A

Given that the allowable tensile stress is 10,844 psi, we can substitute the values into the formula:

Load = 10,844 psi * A

Finally, we need to calculate the deformation caused by the load. We can use Hooke's Law, which states that the deformation of an object is directly proportional to the load applied. The formula for deformation is:

Deformation = (Load * length) / (E * A)

Where E is the Young's modulus of the material, and length is the length of the rod.

Given that E = 30 * 10^6 psi and the length is 24 ft, we can substitute the values into the formula:

Deformation = (Load * length) / (E * A)

Now, we can substitute the values and calculate the maximum load and deformation:

1. Calculate the diameter:
d = 24 ft / π
d ≈ 7.64 ft

2. Calculate the radius:
r = d / 2
r ≈ 7.64 ft / 2
r ≈ 3.82 ft

3. Calculate the cross-sectional area:
A = π * (r^2)
A = π * (3.82 ft)^2

4. Calculate the maximum load:
Load = 10,844 psi * A

5. Calculate the deformation:
Deformation = (Load * 24 ft) / (30 * 10^6 psi * A)

By calculating these values, you can determine the rod that meets the specifications.