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Question: 

The Achilles tendon is attached to the rear of the foot as shown in Fig. 9–73. When a person elevates himself just barely off the floor on the “ball of one foot,” estimate the tension $F_T$ in the Achilles tendon (pulling upward), and the (downward) force $F_B$ exerted by the lower leg bone on the foot. Assume the person has a mass of 72 kg and $D$ is twice as long as $d$.

Problem 36.

Figure 9-73.

Source: Giancoli, Douglas C., Physics: Principles with Applications, 7th Edition, 2014.

Quick Answer: 

$F_T = 1400 \textrm{ N, } F_B = 2100 \textrm{ N}$

Giancoli 7th Edition, Chapter 9, Problem 36

(1:54)

Chapter 9, Problem 36 is solved.

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Comments

why we took the normal force (upward) not the weight (downward)???