Fall factor:

In climbing, the fall factor is the value which defines the severity of a fall, and in
consequence, its degree of risk and the consequences for all the roped party. This theoretical
value lies between 0 and 2 in climbing conditions
The fall factor is calculated by dividing the length of the fall by the length of rope in play.
A/ In the first case, the belayer is at point (a), there is a runner 2.5m above, at point (b). The
climber continues upwards to point (c) , 2.5m above the runner.
The climber falls. His length of fall is 2.5 + 2.5 = 5 metres.
The fall factor will be: 5 m fall distance divided by 5 m of rope in play = 1.
This is a reasonable fall factor.