Chapter 11, Problem 6PCE

BIO Predict/Calculate Force to Hold a Baseball A person holds a 1.42-N baseball in his hand, a distance of 34.0 cm from the elbow joint, as shown in Figure 11-40. The biceps attached at a distance of 2.75 cm from the elbow, exerts an upward force of 12.6 N on the forearm. Consider the forearm and hand to be a uniform rod with a mass of 1.20 kg. (a) Calculate the net torque acting on the forearm and hand. Use the elbow joint as the axis of rotation. (b) If the net torque obtained in part (a) is nonzero, in which direction will the forearm and hand rotate? (c) Would the torque exerted on the forearm by the biceps increase or decrease if the biceps were attached farther from the elbow joint?

Figure 11-40 Problem 6 and 23