Each part and component in the machine is connected to other parts or components around it, so the movement of each part and component is subject to certain limitations. Like the heavy hammer on the lifting shaft of the roving machine, the heavy hammer should have lowered due to gravity, but the chain pulled it, limiting its downward movement.
For example, the roller can only rotate around the support, and the roller stool has a certain limiting effect on the movement of the roller. For a heavy hammer, the chain is the constraint, and for a roller, the roller stool is the constraint. Obviously, the chain restricts the descent of the heavy hammer, exerting a strong force on it. This force acting on an object is called constraint reaction force.
When conducting force analysis on actual mechanisms, it is necessary to analyze and determine the forces exerted on each component, including the active force and constraint reaction force. The main force is predetermined, but the direction of the constraint reaction force is related to the object's constraint situation To analyze based on the specific conditions of the treaty, the magnitude of the constraint is generally unknown and needs to be determined by equilibrium conditions.
When solving mechanical problems, it is necessary to select and determine an object (or a combination of objects) as the research object from many objects related to the problem based on known conditions and the quantity to be solved Perform force analysis on it. In order to clearly represent the force situation of the studied object, it is necessary to separate the research object from the surrounding objects (i.e. release the constraints) Draw it separately. This type of separated object is called a separated body.