Problem 2.10. A woman performs seated machine curls as shown in Fig. 2.12. She performs the exercise slowly so that the acceleration of the weights she lifts can be neglected. If she lifts a weight of 15 kg, deter- 2.7 Problems 55 mine the force exerted by the bar on the woman when her forearm makes 30° with the horizontal axis. Hint: first determine the unit vec- tor along line BD. Answer: F =147 (0.997 e1 -0.07 e2).