Mechanics: It is that branch of scientific analysis which deals with motion, time andforce.

Kinematics is the study of motion, without considering the forces which produce thatmotion. Kinematics of machines deals with the study of the relative motion of machine parts. It involves the study of position, displacement, velocity and acceleration of machine parts.

Dynamics of machines involves the study of forces acting on the machine parts and themotions resulting from these forces.

Plane motion: A body has plane motion, if all its points move in planes which areparallel to some reference plane. A body with plane motion will have only three degrees of freedom. I.e., linear along two axes parallel to the reference plane and rotational/angular about the axis perpendicular to the reference plane. (eg. linear along X and Z and rotational about Y.)The reference plane is called plane of motion. Plane motion can be of three types. 1) Translation 2) rotation and 3) combination of translation and rotation.