The degree of freedom of a joint refers to the number of independent motions or directions in which the joint can move. In the case of a rigid jointed joint plane frame, the degree of freedom can be determined by considering the constraints and restrictions imposed by the joint connections.

Rigid Jointed Joint Plane Frame:

A rigid jointed joint plane frame consists of a series of members connected at their ends by joints. These joints are assumed to be perfectly rigid, meaning that they do not allow any relative movement between the connected members. The frame is typically constructed by welding or bolting the members together at the joints.

Degree of Freedom:

The degree of freedom of a joint in a rigid jointed joint plane frame can be determined using the equation:

DOF = 6 - R - 2J

Where:
DOF = Degree of Freedom
R = Number of reactions or constraints at the joint
J = Number of members meeting at the joint

Explanation:

1. Reactions (R):
The number of reactions at a joint depends on the support conditions. A joint may have both translational and rotational reactions. In a two-dimensional plane frame, each joint can have a maximum of three reactions: two translations (horizontal and vertical) and one rotation. However, the number of reactions can be less if the joint is fully restrained or partially restrained.

2. Members (J):
The number of members meeting at a joint represents the connections between the members. Each member provides two degrees of freedom at the joint, one for each end. Therefore, the total number of degrees of freedom contributed by the members meeting at a joint is equal to twice the number of members.

By subtracting the number of reactions (R) and twice the number of members (2J) from 6, we can determine the degree of freedom (DOF) at the joint.

In the case of a rigid jointed joint plane frame, the joints are assumed to be fully restrained, meaning that all three reactions (R) are present at each joint. Additionally, each joint is connected to two members (J). Substituting these values into the equation, we have:

DOF = 6 - R - 2J
DOF = 6 - 3 - 2(2)
DOF = 6 - 3 - 4
DOF = 3

Therefore, the degree of freedom of a joint for a rigid jointed joint plane frame is 3 (option C).