Static Force Analysis conti....
Four bar mechanism showing external and constraint forces
Constraint forces of action and reaction at a mechanical contact occur in pairs and thus have no net force effect on the system of bodies being considered.
When a part of the body is considered in isolation the effect of such force is considered by using the freebody diagram.
Characteristics of a force are its magnitude, its direction and its point of application
Two equal and opposite forces along two parallel but noncollinear straight lines in a body cannot be combined to constitute a single force and they constitute a couple. The arm of the couple is the perpendicular distance between their lines of action and the plane of the couple is the plane containing the two lines of action.
The moment of the couple M is a vector directed normal to the plane of the couple and the sense of M is in accordance to the right-hand rule for rotation.
The value of M is independent of the choice of the reference point about which the moments are taken, because the vector Rba is the same for all positions of the origin.
As the moment vector M is independent of any particular origin or line of application, hence it is a free vector.
No comments:
Post a Comment