Tension in a rigid body is one of the internal forces described in the previous section. If we imagine trying to bend a rod, what’s happening is that we are trying to make the "outer" part of the bend longer by stretching it. The tension force is the force that is resisting that bend and is keeping the rod straight. On the "innter" part of the bend, there is compression, as that side is being pressed inward.

Ropes have the property that they can only be used for pulling, but not pushing. This leads to a number of interesting physical properties.

The tension in a rope is generally assumed to be the same throughout its whole length. That is, if you were to treat the rope as two pieces being held together by tension, the tension you calculate does not depend on where you choose to break the rope.

As the tension in a rope goes to zero, the rope goes slack and is no longer transmitting any forces.