2.7 Tension

Tension in a cord is defined as the pull (which is a force) that any one part of the cord exerts on the adjacent part. Tension must be taken into account when finding the net force in systems of masses connected by cords (or string, or chains, etc.). Take the following example:

A 20.0 kg block (A) rests on a frictionless table; a cord attached to the block extends horizontally to a pulley at the edge of the table. A 10.0 kg mass (B) hangs at the end of the cord. Calculate a) the acceleration of the block and mass and b) the tension in the cord.

We use two equations to solve both parts a and b, each involving one of the two objects:

Thus, the tension on the rope is 196 N.