Question

What is the shear stress at the neutral axis in a beam of isosceles triangular section with a base of 40 mm and height 20 mm subjected to a shear force of 3 kN?

• A. 3 MPa
• B. 6 MPa
• C. 10 MPa
• D. 20 MPa

Answer 1

The correct option is C 10 MPa

$\because {\tau }_{avg}=\frac{V}{A}$

$\because A=\frac{1}{2}bh=\frac{1}{2}\times 40\times 20$

$=400m{m}^2$

$\therefore {\tau }_{avg}=\frac{3\times {10}^3}{400}=\frac{30}{4}MPa$

$\because {\tau }_{N.A}=\frac{4}{3}{\tau }_{avg}=\frac{4}{3}\times \frac{30}{4}=10MPa$