Question

The large quadriceps muscle in the upper leg terminate at the lower end in a tendon attached to the upper end of the tibia. The forces on the lower leg are defined as: T is the tension in the tendon, w is the force of gravity acting on the lower leg, and F is the weight of the foot.
Find T when the tendon is at an angle of 25o with the tibia, assuming w=120N,F=20Nandthelegisextendedatanangleof40o with respect to the vertical. Assume that the center of gravity of the lower leg is at its center and that the tendon attaches to the lower leg at a point one fourth of the way down the leg

Answer 1

$$-\frac{d}{2}w_y-dF_y+\frac{d}{4}T_y=0$$

$$-\frac{d}{2}w\sin{\theta}-dF\sin{\theta}+\frac{d}{4}T\sin{\theta'}=0$$

$$-\frac{1}{2}120\sin{40}-20\sin{40}+\frac{1}{4}T\sin{25}=0$$

$$T=487\ N$$