Problem P4.15 Gripper C of the industrial robot is accidentally subjected to a 60 -lb side load directed perpendicular to BC (Figure P4.15). The lengths of the robot\'s links are AB = 22 in. and BC = 18 in. By using the moment components method, determine the moment of this force about the center of joint A. Solution It is given that AB is making an angle of 15 with horizonatal and BC is making an angle of 40 with AB therefore the angle of BC with the horizontal will be 55 and 60 lb force is perpendicular to the BC therfore it will make an angle of 35 with the horizontal.So we will breakinto components along horizontal and vertical as shown in the figure. Now we will calculate the perpendicualr distance between the forces and point A. Perpendicular distance of point A from 60Sin35 will be equal to = AD +BE = 31.57 Perpendicular distance of point A from 60Cos35 will be equal to = BD + CE = 20.43 Now from the right angle triangle ABD and BCE we will calculate the value of AD = 21.25 , BE = 10.32, BD = 5.69 , CE = 14.74 Now the moment at point A due to 60Sin35 will be = 60sin35*31.57 (anticlockwise) Due to 60Cos35 = 60Cos35*20.43 (Anticlockwise) Since the nature of moment of both the forces is same therefore they will be added Net moment at point A = 2090.58 lb-in.