Question

The force of gravity acting on the arm acts through point A. Assume that L₁ = 0.0820m, L₂ = 0.290m and = 13.1^o. Determine the magnitude of the tension force F_t in the deltoid muscle.

6.07×10² N

Determine the magnitude of the tension force F_s of the shoulder on the humerus (upper-arm bone) to hold the arm in the position shown.

6.00×10² N

Determine the angle of tension force F_s relative to the x-axis?

Answer 1

using equilibrium of torque about O

F_t Sin13.1 (L₁) = F_g L₂

F_t Sin13.1 (0.082) = F_g (0.290)

F_t = 15.6 F_g (value of F_g not given in the question)

using equilibrium of force in horizontal direction

F_t Cos13.1 = F_s Cos eq-1

using equilibrium of force in vertical direction

F_t Sin13.1 - F_g = F_s Sin eq-2

taking the ratio of eq-1 and eq-2

tan = (F_t Sin13.1 - F_g )/Cos13.1