Question

A person who weighs 764 N supports himself on the ball of one foot. The normal force N = 764 N pushes up on the ball of the foot on one side of the ankle joint, while the Achilles tendon pulls up on the foot on the other side of the joint. The center of gravity of the person is located right above the tibia. A. What is the tension in the Achilles tendon? If the force acting is upward, enter a positive value and if the force acting is downward, enter a negative value. (N) B. What is the magnitude of the downward force exerted on the ankle joint by the tibia? (N)

Answer 1

A. 2125.91 N

B. 2889.91 N

Explanation:

A.

Balacing moment,

`\begin{gathered} F_{\text{achiles}}\cdot d_1=N\cdot d_2 \\ F_{\text{achiles}}\cdot4.6=N\cdot12.8 \\ F_{\text{achiles}}=(764\cdot12.8)/(4.6) \\ F_{\text{achiles}}=2125.91\text{ N} \end{gathered}`

B.

Balacing forces,

`\begin{gathered} F_{\text{tibia}}=F_{\text{achiles}}+N_{} \\ \text{ replacing} \\ F_{\text{tibia}}=2125.91+764 \\ F_{\text{tibia}}=2889.91\text{ N} \end{gathered}`