Problem 4
A person weighs 80 kg is lifting his body on a single leg, while maintaining a stable position, as shown below. Considering the foot and ankle free body diagram, shown below,
1. Estimate the force on the ankle joint for the position shown below.
2. If the height of the heel from the ground is zero, i.e. the heel is touching the ground, what will be the force on the ankle joint? Prove that mathematically.
Note:
1. Assume a full static equilibrium.
2. Consider the weight of the body as the only external load applied.
3. $F_A$: muscle force
$F_P$: force on the ankle joint