GOAL Apply the equilibrium conditions to the human body.Humerus50.0 N- BicepsUlna-0.0300 m50.0 N0.0300 m0.350 m0.350 m(a) A weight held with the forearm horizontal. (b) The mechanical model for thesystemPROBLEM A 50.0-N (11-lb) bowling ball is held in a person's hand with the forearmhorizontal, as in Figure (a). The biceps muscle is attached 0.0300 m from the joint, and theball is 0.350 m from the joint. Find the upward force F exerted by the biceps on the forearm(the ulna) and the downward force R exerted by the humerus on the forearm, acting at thejoint. Neglect the weight of the forearm and slight deviation from the vertical of the biceps.STRATEGY The forces acting on the forearm are equivalent to those acting on a bar oflength 0.350 m, as shown in Figure (b). Choose the usual x- and y-coordinates as shown andthe axis at O on the left end. (This completes Steps 1 and 2.) Use the conditions ofequilibrium to generate equations for the unknowns, and solve.SOLUTIONApply the second condition forequilibrium (Step 3) and solve forthe upward force F.ET; = TR+ TF+ TBB= 0R(0) + F(0.0300 m) - (50.0 N)(0.350 m) = 0F = 583 N (131 Ib)EF, = F-R - 50.0 N = 0R = F- 50.0 = 583 N - 50 N = 533 N (120 Ib)Apply the first condition forequilibrium (Step 4) and solve(Step 5) for the downward forceR.LEARN MOREREMARKS The magnitude of the force supplied by the biceps must be about ten times aslarge as the bowling ball it is supporting!QUESTION Suppose the biceps were surgically reattached three centimeters farther towardthe person's hand. If the same bowling ball were again held in the person's hand, how wouldthe force required for the biceps be affected? Explain? (Select all that apply.)O It would require more force because of the larger distance between the elbow and thelocation where the force from the biceps acts.O It would require more force because the force is less nearly perpendicular to themoment arm.O It would require less force because of the larger distance between the elbow and thelocation where the force from the biceps acts.O It would require more force because the force acts closer to the heavy bowling ball.O It would require less force because the torque for each newton of force from the bicepsis greater. PRACTICE ITUse the worked example above to help you solve this problem. A W = 51.7 N (11.6 Ib) weightis held in a person's hand with the forearm horizontal, as shown in the figure. The bicepsmuscle is attached d = 0.03005 m from the joint, and the weight is l = 0.349 m from the joint.Find the upward force F exerted by the biceps on the forearm (the ulna) and the downwardforce R exerted by the humerus on the forearm, acting at the joint. Neglect the weight of theforearm.F =R =EXERCISEHINTS: GETTING STARTED | I'M STUCK!Use the values from PRACTICE IT to help you work this exercise. Suppose you wanted to limitthe force acting on your joint to a maximum value of 8.44 x 102 N.(a) Under these circumstances, what maximum weight would you attempt to lift?N(b) What force would your biceps apply while lifting this weight?

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Accepted Answer

In an equilibrium position, the net force acting on the system is zero. It means this the system is…