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 to maintain static equilibrium in this plane.
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