Consider Figure $2$: Here ${}_1$ is the elbow joint angle, ${}_2$ is the insertion angle of the Biceps muscle, $l_1$ is the distance of insertion of the biceps muscle from the elbow joint, $l_2$ is the distance between the elbow joint and the $CG$ of the lower arm $+$ hand segment and $l_3$ is the length of the lower arm $+$ hand segment. Let $l_1=5cm,l_2=15cm$&$l_3=35$ cm $.$ Weight of Upper arm and Hand segment $=15N.$

Assume that there is no motion at the joint $($i$.$e$.$ the joint is stationary$),$ draw the FBD$,$ write the equations of static equilibrium and find out the joint reaction forces for the following cases: a$){}_1=90$&${}_2=90,$ b$){}_1=90$&${}_2=85,$ c$){}_1=120$&${}_2=90$ d$){}_1=120$&${}_2=85$ and e$)$ Consider that the person holds an object of mass $10$ Kgs in the hand. Repeat the analysis for parts $b$&$d$ for this condition.