Question

A bicep curl is performed where the (CoM) of the dumbbell is 0.350 m from the joint (pivot). Assuming that the mass of the arm is 7 kg and acts 0.20 m from the joint, and the biceps tendon acts at a distance of 0.015 m from the joint, what magnitude of force in newtons (N) must the biceps tendon produce to lift the 15 kg mass? The arm is at an angle of 15 degrees above the horizon. The given distances from the joint are the distances along the line that is 15 degrees above the horizon)

Answer 1

F = ? F _1 = 7kg. wt = 7 times 9. 81N = 68. 67N F _2 = 15kg. wt = 15 times 9. 87 = 147. 15N therefore moment of force tau = F _1l _1 cos theta + F _2l _1cos theta + F _2 l _2 cos theta tau = 68. 67 times 0. 20 times (15 degree) + 147. 15 times 0. 350 cos 0 = 13. 27 + 49. 75 = 63. 02Nm force on tendon, F = tau/x = 63. 02/0. 015 = 4201. 17N