You hold a 1.80-N softball in your hand as shown in the figure. Consider your fo

Question

You hold a 1.80-N softball in your hand as shown in the figure. Consider your forearm and hand to be a uniform rod with a mass of 1.40 kg and the distance between the elbow joint and the ball in your hand is 2L = 28.0 cm.Your biceps exerts an upward force of 12.0 N on the forearm and is attached at a distance of d = 2.40 cm from the elbow.

(a) Using the elbow joint as the axis of rotation, determine the magnitude of the net torque acting about the elbow due to the forearm, hand, and ball.
__________N

Explanation / Answer

torque due to the ball = Q1 = -mg*2L = -1.8*0.28 = -0.504 Nm (clockwise)

torque due to the forarm+hand = Q2 = -Mg*L = -1.4*9.8*0.14
= -1.9208 Nm (clockwise)

torque due to the biceps = Q3 = +F*d = +12*0.024 = +0.288 Nm ( counter clockwise)

total torque = Q = Q1 + Q2 +Q3 = -0.504 - 1.9208+0.288 = -2.1368

part b)

net toeque is negative

the forearm will rotate in clockwise direction

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