balance each other

produce a couple and an unbalanced force

are equivalent

can not balance each other.

2n-3

n-l

′2n-l

n - 2

resultant couple

moment of the forces

resulting couple

moment of the couple

two members with unknown forces of the frame

three members with unknown forces of the frame

four members with unknown forces of the frame

three members with known forces of the frame

the center of heavy portion

the bottom surface

the mid point of its axis

all of the above