Answer:
The stress of the steel bar is 5.97 N/mm^2.
Step-by-step explanation:
To calculate the stress of the steel bar, we can use the formula:
stress = force/area
where force is the stretching force applied to the bar and area is the cross-sectional area of the bar. The cross-sectional area can be calculated using the diameter of the bar as:
area = π/4 * diameter^2
Substituting the given values, we get:
area = π/4 * (80mm)^2 = 5026.55 mm^2
(Note that we converted the diameter to millimeters to keep the units consistent.)
Now, we can calculate the stress as:
stress = force/area = 30 kN / 5026.55 mm^2 = 5.97 N/mm^2