Finding the force applied on a foot

[chris_0101]

So this is the question summarized:
Mass of the person is 75kg, the person is standing on his/her tiptoes. There are three forces acting on the foot which are:
-Upward Normal force from toes - Calculated to be mg=735N (Fn)
-Downward force from ankle onto foot (Fa)
-Upward force from tibia to foot (Fb)

The distances between each point are:
-Distance between toes and ankle is 12.5cm
-Distance from ankle to tibia is 6.5cm

Basically, I have to figure out the magnitudes of Fa and Fb, but I'm not too sure how to complete it.

I do know that it is an equilibrium situation where:

Fa + Fb + Fn = 0

But I do not know how to find Fa and Fb.

The answers of Fa and Fb are 706N and 1073N respectvely.

If anyone could shed some light on this, it would be great.

 

[gneill]

Can you draw and post a diagram with the forces labeled? I can't quite picture the upward force applied by the tibia...

 

[ashishsinghal]

also consider the rotational equilibrium

 

[ashishsinghal]

provide fbd as the question is quite unclear