When the Vector Sum of Three Co-Planar Forces

Multiple Choice

When the vector sum of three co-planar forces, , and , is parallel to , we can conclude that and

A) must sum to zero.
B) must be equal and opposite.
C) must have equal and opposite components perpendicular to
.
D) must have equal and opposite components parallel to
.
E) must have equal and opposite components parallel and perpendicular to
.