Answer
The force is 35 times the weight of the leg.
Work Step by Step
We first find the energy the leg has before it hits the ground:
$E=mgh=(8)(9.81)(.7)\approx 55J$
We know that the force is equal to the work done over the distance. Thus, we find:
$F = \frac{55J}{.02m} = 2,749 \ N$
Thus, the force is 35 times the weight of the leg.
