Question

Which one is not the condition for the equilibrium in free body diagram for calculation of the normal forces along the body kept over the wedge, consider all forces to be straight and linear?

(a) ∑Fx=0

(b) ∑Fy=0

(c) ∑Fz=0

(d) ∑F≠0

This question was addressed to me during an internship interview.

This key question is from Wedges topic in chapter Friction of Engineering Mechanics

Answer 1

Correct choice is (d) ∑F≠0

The explanation: For the equilibrium in the three dimensional system of axis we have all the conditions true as, ∑Fx=0, ∑Fy=0 and ∑Fz=0. Also, we have the summation of the forces equal to zero. Which is not a non-zero value.