Question

The span of cantilever beam is 2 m. The cross-section of the beam is a hollow square with external sides 100 mm; and its $I=4\times {10}^{5}m{m}^4$. The safe bending stress for the beam material is $100N/m{m}^2$. The safe concentrated load at the free end would be

• A. 100 N
• B. 200 N
• C. 300 N
• D. 400 N

Answer 1

The correct option is D 400 N

Max. bending stress,

$\sigma =\frac{M}{Z}=\frac{PL}{Z}$

$Z=\frac{I}{y_{max}}=\frac{4\times {10}^5}{50}=8\times {10}^{3}m{m}^3$

$\therefore P=\frac{\sigma Z}{L}=\frac{100\times 8\times {10}^3}{2\times 1000}=400N$