If a cantilever beam of length 200 mm is subjected to load of 50 N at a distance of 120 mm from the fixed end of the beam. What is the maximum bending stress developed if section modulus is Zc?

For a cantilever beam, maximum bending stress occurs at the fixed end where bending moment is maximum. The bending moment M at the fixed end equals the load multiplied by the distance from the fixed end: M = 50 N x 120 mm. Bending stress is given by sigma = M/Zc, where Zc is the section modulus. Therefore sigma = (50 x 120)/Zc. Option A incorrectly uses the denominator format, option B uses the wrong moment arm (80 mm would be the distance to the free end), and option C incorrectly multiplies by Zc instead of dividing.