Theory of Machines

Definition
Theory of Machines is a branch of science dealing with the study of relative motion between the various parts of a machine and forces which act on them. Theory of Machines has two sub branches namely Kinematics and Dynamics.

Kinematics deals with the study of relative motion between the various parts of a machine. The force which act on them would be static in nature.

Dynamics deals with the study of relative motion between the various parts of a machine. The force which act on them would be static or dynamic in nature. Dynamics has two sub branches namely Kinetics and Statics.

Kinetics is a branch of theory of machine which deals with various forces when the body is moving whereas Statics is a branch of theory of machine which deals with various forces when the body is stationary.

Mechanism
Mechanism is a combination of rigid or restraining bodies which are so shaped and connected that they move upon each other with definite relative motion.

Machine
A machine may be defined as an assemblage of resistant bodies whose relative motions are successfully constrained so that some form of natural energy may be modified or transmitted to do some special kind of work.

A machine is a mechanism or a combination of mechanisms which not only imparts definite motions to the parts but also transmits and modifies the available mechanical energy into some kind of useful energy. This useful energy may be in the shape of some kind of desired work. The slider-crank mechanism will become a machine when it is being used in automobile engine by adding valve mechanism. Here it will convert the available energy which is force on the piston into desired energy which is torque on the crankshaft. This torque will enable the movement of the vehicle.

Link
A link is defined as a member or combination of members, connecting other members and having motion relative to them. A slider crank mechanism consists of the following four links. 1. Frame, 2.Crank, 3. Connecting rod, 4. Slider

Kinematic Pair
Kinematic pair is a joint of two links having relative motion between them.