7.1 A 3 m long steel bar has a diameter of 80 mm - NSC Technical Sciences - Question 7 - 2021 - Paper 1

To calculate the stress ( ( \sigma ) ) in the steel bar, we use the formula:

$\sigma = \frac{F}{A}$

where:

• ( F ) is the force applied (30 kN) = 30,000 N
• ( A ) is the cross-sectional area of the bar, calculated as:

$A = \frac{\pi d^2}{4}$

Given the diameter (( d )) is 80 mm, we convert this to meters: ( d = 0.08 , m )

Now, calculating the area:

$A = \frac{\pi (0.08)^2}{4} = 5.027 \times 10^{-3} \, m^2$

Substituting the values into the stress formula:

≈ 5,967,774.02 \, Pa$$ Thus, the stress of the steel bar is approximately 5,967,774.02 Pa.