Since the belt continuously runs over the pulleys, therefore, some centrifugal force is caused, whose effect is to increase the tension on both, tight as well as the slack sides. The tension caused by centrifugal force is called centrifugal tension. At lower belt speeds (less than 10 m/s), the centrifugal tension is very small, but at higher belt speeds (more than 10 m/s), its effect is considerable and thus should be taken into account.

Consider a small portion PQ of the belt subtending an angle dq the centre of the pulley as shown in Fig.

The belt continuously runs over both the pulleys. In tight side and slack side of belt tension is increased because of presence of centrifugal Tension in belt. At lower speeds centrifugal tension can be ignored but at the higher speed its effect is considered.