Ropes Climbing ropes can be divided into two groups by their relative elasticity: "Static Ropes" and "Dynamic Ropes".  Static ropes have low static elasticity (1%-4%). This is useful for repelling, and climbing with a fixed anchor above the climber, when the falls are relatively small. But using it for more intense falls will result in high forces acting on the climber. Dynamic ropes, on the other hand, have a bigger elasticity (6%-10%). They are the main ropes used for climbing, as they stretch more, and thus provide more cushioning for the fall. (http://www.theuiaa.org/) The diagram to the right shows the standard UIAA test for the maximum force on ropes. In the test a 80kg weight (for single ropes, 55kg for half ropes) undergoes a fall with 1.77 fall factor. As the maximum force from this fall is published, we can calculate k for a given rope: So: For example, a typical single rope's maximum force (from the test) is about 9 kN. From this, we can calculate k: We take this to a wide range of problems, for example: We can calculate the maximum weight of a climber undergoing a fall factor of 2, so that the system doesn't undergo dangerous forces of more than 12kN. This model is a very good estimate, but it has it's limitations.