4. Consider again Fig. 1.12. Now let the 14-kg weight hang from the middle of the lower arm (20 cm from the fulcrum). Calculate the biceps force and the reaction force at the joint.
5. Consider the situation when the arm in Fig. 1.13 supports two 14-kg weights, one held by the hand as in Fig. 1.13 and the other supported in the middle of the arm as in Exercise 1-6. (a) Calculate the force of the biceps muscle and the reaction force.
6. Calculate the additional forces due to the weight of the arm itself. Assume that the lower part of the arm has a mass of 2 kg and that its total weight can be considered to act at the middle of the lower arm, and 14 kg hanged in the hand.