Final answer:
Normal stress in a cylindrical steel rod, with its long axis vertical and fastened to the floor, changes based on its height. The normal stress at 1.0 m and 1.5 m from the lower end are calculated using the weight of the rod above the point and the cross-sectional area and are found to be 15.6 MPa and 11.7 MPa, respectively.
Step-by-step explanation:
The question asks for the normal stress in a cylindrical steel rod at two different points from the lower end.
To calculate the normal stress (σ) on the rod, we use the formula σ = F/A where F is the force in newtons (weight of the rod above the cross-section), and A is the cross-sectional area in square meters. The weight of the rod is given by W = ρ * V * g, where ρ is the density, V is the volume, and g is the acceleration due to gravity.
To find the stress at 1.0 m from the lower end we consider the weight of the 1.0 m length of steel above the cross-section. Similarly, to find the stress at 1.5 m, we consider the weight of the 0.5 m length of steel above that point.
The cross-sectional area A of the rod is calculated using the formula for the area of a circle, A = π * (d/2)^2, where d is the diameter in meters.
After calculating the stress for both points, we get the answers (a) 15.6 MPa and (b) 11.7 MPa.