I was having a lot of trouble understanding tension force in a string. So i decided to write a sort of essay on it. Here it is: Tension/Tension Force 1.Tension/Tension force is the electromagnetic internal force transmitted through a rope, string, cable or a wire, when pulled taut by external forces. 2. It actually refers to an action and reaction pair of force, the action force being responsible for maintaining equilibrium of the string(actually the particles) and the reaction one being responsible for transmitting the force to the other end of the string. 3. Strictly speaking tension has no general direction but for a particular object a direction may be assigned. It is directed along the rope. 4.For different objects in a system, the direction of tension is different. To find the direction of tension for an object we draw the FBD of the body and then find the tension force for the body (the force among the two forces which acts on the body). 5.Strings, cables, ropes, etc. all consist of atoms. The distance between two atoms is called the interatomic distance. For a particular value of interatomic distance there exists no force between one atom and the adjacent atom. When the I.D. is greater than this value, there exist attractive forces between the two atoms (action force by the 2nd last atom on the last atom to bring it back to its initial position and reaction force exerted by the last atom on the 2nd last atom to transmit the force). 6.Thus the force applied at one end of the rope gets transmitted from one end of the rope to the other end of the rope without the rope breaking. |<-.-> <-.-> <-.-> <-.-> <-.->F (The dots represent the particles making up the string and the arrows represent the forces acting on the particles. 7.When stating the value of tension force for a particular point in a rope, the value of the force except the transmitting force is stated. 8.For simplification of problems, the net force acting on the string is required to be zero. And there should be no loss of energy through friction. Also the string should be rigid and inextensible. Therefore, it is considered massless, inextensible and frictionless. For a massless rope, Mass=0 Net Force=mass x acceleration =>Net Force=0 Also acceleration is taken to be zero though it may have a non-zero value. (It is indeterminate) The questioning of the acceleration of the string defeats the purpose of making the rope massless. Tension in a massless rope is same throughout. For a rope having mass, Mass ≠ 0 Net Force = mass x acceleration =>Net Force and acceleration = 0 or Net Force and acceleration ≠ 0 That is the acceleration is zero if net force is zero and the acceleration is non-zero if net force is non-zero. Tension in a rope having mass is not same throughout. Since the mass of the rope is also pulled. Rope->Massless->Net force on rope=0 Rope->Has mass->Net force on rope and acceleration may be 0 or may not be 0. Note : The tension in a string may be due to the application of external opposite forces at the ends of the rope or due to the application of external force at one end of the rope, the other end being attached to an object. On any segment of rope, the forces acting are the force applied and the tension force. To find the value of tension we equate two expressions for net force acting on the required segment of the rope. My question is that is this description of tension force correct?