Frequently, attention in an equilibrium situation is confined to a plane. An example would be a ladder leaning against a wall, which is in danger of slipping only in the plane perpendicular to the ground and wall. By orienting a Cartesian coordinate system so that the x and y axes are in this plane, choose which of the following sets of quantities must be zero?
a. ∑Fx and ∑τz and ∑Fy
b. ∑Fz and ∑τx and ∑τy
c. ∑τx and ∑Fx and ∑τy and ∑Fy
d. ∑τx and ∑Fx and ∑τy and ∑Fy and ∑τz