How Do Forces Balance When Standing on Tiptoe?

[wowdusk]

Homework Statement

When a person stands on tiptoe (a strenuous position), the position of the foot is as shown in Figure P8.16a. The total gravitational force on the body, Fg, is supported by the force n exerted by the floor on the toes of one foot. A mechanical model of the situation is shown in Figure P8.16b, where T is the force exerted by the achilles tendon on the foot and R is the force exerted by the tibia on the foot. Find the values of T, R, and theta when Fg = 700 N.

for the picture go here http://qaboard.cramster.com/physics-topic-5-1064-cpi0.aspx

Figure P8.16

Homework Equations

The Attempt at a Solution

i'm really confused...

 

[tiny-tim]

The total gravitational force on the body, Fg, is supported by the force n exerted by the floor on the toes of one foot. A mechanical model of the situation is shown in Figure P8.16b, where T is the force exerted by the achilles tendon on the foot and R is the force exerted by the tibia on the foot. Find the values of T, R, and theta when Fg = 700 N.

Hi wowdusk!

n = F_g = 755N (or is it 700N? I'm confused ).

The foot is in equilibrium, so everything should add to zero.

Take components of force vertically and horizontally, and also take moments of force about some point (I suggest the end of the R force).

What equations do you get?