A 2.0m light rod lies along the +x-axis and is pivoted at its left end. A 10N force is applied in each scenario below. In which case is the torque about the pivot equal to zero?
a) Applied at the right end, directed straight to the right (+x).
b) Applied at the right end, directed straight upward (+y).
c) Applied 0.50m from the pivot, directed straight upward (+y).
d) Applied at the rod’s midpoint, directed straight downward (−y).