Impact Force (כוח בלימה) or in short: IF is the maximum value that is generated while breaking a lead fall. Obviously, the higher the impact force, the more potentially harmfull the fall is. Computation of the Impact Force is complicated, but it it rises with the Fall Factor, which is easy to estimate, even during a climb.
The fied dealing with analysis, computing and estimation of the breaking forces, fall factors and their relations is called fall dynamics.
The force that is applied to the rope during the arrest of a falling climber is not constant. It rises up to a maximum value and then drops again (usually with some bobbing) until it stabilises on the climbers weight. The definition of the Impact force refers to the maximum value only, but the ammount of energy absorbed, and the time needed to arrest the fall (and to absorb that energy) are also important.
Contributions to this page by: Micha Yaniv and others