COUPLE OF FORCE
COUPLE OF FORCE
Two forces which are equal in magnitude but opposite in direction and not acting along the same line constitute a couple.
Consider two equal and opposite forces F and -F acting oppositely along parallel lines on two points A and B as shown below: Let and are their position vectors with respect to origin.
Magnitude of torque is given by:
Where q is the angle between and . rsinq is the perpendicular distance between the line of action of the two forces. Let it is denoted by d. Thus the magnitude of the torque of couple will be:
Where d is called the moment arm of the couple. Now
the magnitude of the couple = Magnitude of any of the forces forming couple X moment arm of couple