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Climber injured in bluies after 30m fall 2/Jan/13 21-Jan-2013 At 11:38:56 PM jakob

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I stated that you couldn't get a fall factor above 2, however I have been corrected by the very unlikely scenario that the belayer is taking in as you are falling!!! If this were the case, then, yes, you might get slightly over FF2.

If the belayer has slackness in the rope, then as someone else has mentioned, this reduces the fall factor and the forces involved. Tightness in the rope results in greater forces albeit the climber falls less of a distance.

Someone discussed the possibility of the belayer having slackness between them and the anchor such that in a fall, the belayer themself was moved. Whilst technically you could say this is a greater than a fall factor 2, just remember why we as climbers talk about FF2's, its to understand the forces involved due to the deceleration of the climber. In the scenario where the belayer is moved this actually bleeds off energy from the fall, decelerating your climber. Energy is conserved in the system, and your belayer is consuming your fall energy (through the violent movement towards the edge of the ledge) that would otherwise have been absorbed by your anchors/rope etc.

The calculation made before equating MGH to a force was wrong, this calculates gravitational potential energy. To calculate force you need to know the distance over which deceleration occurred (indicative by rope stretch).

As an example, if you assume a 30m clean fall (i.e. hanging belay), 15m above the last piece of protection, with a 100kg climber, using a rope that has 20% rope stretch, assuming uniform deceleration (which is probably unlikely), then the force will be:
Force = Gravitational Potential / Deceleration Distance
(100kg*30m (fall length)*10m/s/s) / (30m (rope paid out) *20%) = 5kN.

If you have a nice new rope that has 30% stretch, the force is reduced to 3.3kN.

From above you can see that if the belayer was to be moved by the supposed greater than FF2 due to a slackness between belayer and anchor, then this increases the deceleration distance and reduces the forces involved.

If as I suspect I am wrong about uniform deceleration (ropes don't bounce like a bunjy jump), then the force will be significantly higher then the examples above (at a guess, 50% higher?), however the above is useful for comparing different fall types, etc.