Respuesta :
Answer:
the average normal stress in the bar is : [tex]\mathbf{\sigma = (32.5 - 20x )MPa}[/tex]
Explanation:
The free body flow of the missing diagram is attached to the answer below.
From the information given:
Let consider the sum of forces along horizontal direction to be equal to zero.
[tex]\begin{array}{l}\\\sum {{F_x}} = 0\\\\3 + 8\left( {1.25 - x} \right) - N = 0\\\\N = \left( {13 - 8x} \right){\rm{ kN}}\\\end{array}[/tex]
The average normal stress in the bar can be calculated by the formula:
[tex]\sigma = \dfrac{N}{A}[/tex]
where;
[tex]\sigma =[/tex] average normal stress in the bar
A = cross sectional area in the bar and it is given by: [tex]400*10^{-6 } m^2[/tex]
​N = (13- 8x) kN
∴ [tex]\sigma = \dfrac{(13-8)x}{400*10^{-6} m^2}[/tex]
[tex]\sigma = (32.5 - 20x )*10^3 kPa[/tex]
[tex]\sigma = (32.5 - 20x )MPa[/tex]
Thus; the average normal stress in the bar is : [tex]\mathbf{\sigma = (32.5 - 20x )MPa}[/tex]

The average normal stress in the bar as a function of x is equal to 32.5 - 20x MPa.
Given the following data:
- Cross-sectional area of bar = [tex]400 \times 10^{-6}\;m^2[/tex]
- Range of x = 0.5 m < x ≤ 1.25 m.
- Force A = 3 kN.
- Force B = 8(1.25-x) kN.
To calculate the average normal stress in the bar as a function of x.
How to calculate average normal stress.
First of all, we would determine the sum of the forces acting on the bar in the horizontal direction;
[tex]\sum F_x=0\\\\3+8(1.25-x)-N=0\\\\3+10-8x-N=0\\\\13-8x-N=0\\\\N=(13-8x)\; kN[/tex]
For the average normal stress:
Mathematically, the average normal stress is given by this formula:
[tex]\sigma = \frac{N}{A}[/tex]
Where:
- A is the cross-sectional area.
- N is the resultant force.
Substituting the parameters into the formula, we have;
[tex]\sigma = \frac{(13-8x) \times 10^3}{400 \times 10^{-6}}\\\\\sigma = \frac{(13-8x) \times 10^{3+6}}{400}\\\\\sigma =(32.5-20x) \times 10^{9}[/tex]
Note: 1 MPa = [tex]1\times 10^9\;Pa[/tex]
Average normal stress = 32.5 - 20x MPa.
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