Tension in a string:

Tension in a string:

Tension is a force exerted by a string on a body to which it is attached. When we fly a kite we feel some force exerted on our fingers. If we stretch a string tightly the hand will experience force acting towards each other. Similarly if a person is holding a block of weight W by means of a string, the weight of the block pulls it downwards, while the string pulls it upwards with an equal force. The force enerted on the fingers, the force experienced by the hands and the upward force acting on the block is due to the force developed in the strings in each case. This force is called the tension in the string.

The hand experiences a pull in the downward direction at point B. Hence the tension at this point is downwards. However, at point A the string must exert a force upward to balance the weight of the body. Hence the direction of tension is upwards at point A. Thus the direction of tension changes but the magnitude of the tension remains constant at all points in the string. When the block is stationary, the magnitude of tension is equal to the weight of the block suspended from string. The S.I. unit of tension is newton.