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Arm torque A horizontally outstretched arm supports a
Chapter 10, Problem 58E(choose chapter or problem)
Arm torque A horizontally outstretched arm supports a weight of20 lb in a hand (see figure). If the distance from the shoulder to the elbow is 1 ft and the distance from the elbow to the hand is 1ft, find the magnitude and describe the direction of the torque about (a) the shoulder and (b) the elbow. (The units of torque in this case are ft-lb.)
Questions & Answers
QUESTION:
Arm torque A horizontally outstretched arm supports a weight of20 lb in a hand (see figure). If the distance from the shoulder to the elbow is 1 ft and the distance from the elbow to the hand is 1ft, find the magnitude and describe the direction of the torque about (a) the shoulder and (b) the elbow. (The units of torque in this case are ft-lb.)
ANSWER:
Solution 58EStep 1 of 2:The given figure is ; 1. We need to find the torque about the shoulder.The direction of the shoulder can be considered as the positive direction of y - axis .So , = ( 1+ 1)ft = 2j (ft) and F = -20k (lb)We know that , = = 2j = -40( j = - 40i , since ( j = i , ( i = k , and ( k = j Therefore , = -40i.Therefore , the magnitude of is 40 ft - lb and it is directed along the negative x-axis.