Question

A bar, having a 1000 $mm^2$ cross-sectional area, is subjected to axial loads as shown in the figure. What is the value of stress in the QR section?

• A. 30 MPa Compressive
• B. 30 MPa Tensile
• C. 50 MPa Compressive
• D. 50 MPa Tensile

Answer 1

Answer:

A. 30 MPa Compressive

Consider a section in PQ, QR and RS segment respectively and find the load acting on these segments by the algebraic sum of loads on either side of the section considered. $P_{PQ} = 50 kN, P_{QR} =50-80=- 30 kN, P_{RS} =-10 kN; Now for the bar QR,$

$\sigma_{QR} =\frac {P_{QR}} {A} =\frac {-30\times 1000}{ 1000} =-30 MPa$