Topic: Mechanics of Materials
A cantilever beam of rectangular cross section (d x b) is subjected to a shear force 'F'. Which of the following is TRUE?
- A. The beam has a uniform shear stress F/bd
- B. Maximum shear stress and maximum bending stress are equal when L=d/2
- C. For L > d/2, bending stress decides the failure
- D. Bending stress is independent of 'b'
Answer: C. For L > d/2, bending stress decides the failure
Explanation: The maximum shear stress is 1.5 * (F/A) and the maximum bending stress is (FL * d/2) / I. As the length L increases, the bending stress increases linearly while the shear stress remains constant, making bending the dominant failure mode for longer beams.