文档介绍：Statics
静力学
力偶
PART3 Couples
Bilingual Edition
Couples
1 Definition
PART THREE
Two parallel, noncollinear forces that are equal in magnitude and opposite in direction are known as a couple
The two forces of equal magnitude F are oppositely directed along lines of action that are separated by the perpendicular distance d. the lines of action of the two forces determine a plane that we call the plane of couple.
Couples
Real samples
PART THREE
Couples
2 Moment of a couple about a point
PART THREE
Moment of a couple about a point is a value of scalar(标量)
Symbol: counterclockwise “+”; clockwise “-”
hint: The moment of a couple about a point O is independent of the location of O
Couples
3 Characteristics of couple
PART THREE
From the foregoing discussion, we see that a couple possesses two important characteristics:
1. A couple has no resultant force;
2. The moment of a couple is the same about any point in the plane of couple.
Couples
4 Equivalent couples
PART THREE
Because a couple has no resultant force, its only effect on a rigid body is a moment, for this reason, two couples that have the same moment are said to be equivalent.
Couples
4 Equivalent couples
PART THREE
Four operations may be performed on a couple without changing its moment:
Rotating the couple in its plane
Chang