Chapter 09, Problem 22 Your answer is partially correct. Try again A man hold; a

Question

Chapter 09, Problem 22 Your answer is partially correct. Try again A man hold; a 151 N bal in his hand, with the forearm horizontal see the figure . He can support the ball n this position becase of the exor musc·force J hich is applied perpendi ularte eforea m Tha r ar e h, a and has a center of gravity as indicated. Find (a) the magnitude of and the (b) magnitude and (e) direction (as a positive angle counterclockwise from horizontal) of the force applied by the upper arm bone to the forearm at the elbow jeint Upper arm Flexor muscle Elbow joint : 0.0890 m 0.330 m 0.0510 m 864.7 Click if you would like to Show Work for this question:

Explanation / Answer

You have done the first two parts correct, lets verify it.If arm is balanced it means the net moment about elbow is zero.

0.0510*M - (0.0510+0.0890)*22.3-0.330*151=0

M = 1038.27 N

Now forces must be balanced in both horizontal and vertical direction.
Lest say Upper arm applies Fx towards right and Fy upwards
since there is no horizontal force, Fx=0

Now balance forces in vertical direction

Fy+M - 151-22.3=0
Fy = 151+22.3-1038.27
Fy = - 864.97. N
It means force is acting in down direction at the elbow.
Angle is measured counterclockwise from horizontal, angle=90+90+90

So Magnitude is 864.97 N and Angle is 270o

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