Hanging from a rope
If an object hung from a rope stays still, the reason is that a force equal to the weight of the object acts upward along the rope.
Figure to be added
The force the rope produces upward is called the tension in the rope. The weight of the object and the tension in the rope hold the object in equilibrium, so the object stays still.
One story, several names
In all three cases we have seen, the weight is balanced by a single upward force. Only the name given to that force changes from case to case.
| Situation | The upward force | Produced by |
|---|---|---|
| Hanging from a spring balance | The force of the spring | The compressed spring |
| Hanging from a thread or rope | Tension | The stretched rope |
| Resting on a surface | Normal reaction | The bent surface |
In all three the force is equal in magnitude to the weight, opposite to it in direction, and along the same line of action.