A man holds a 171-N ball in his hand, with the forearm horizontal (see the figur
ID: 2029672 • Letter: A
Question
A man holds a 171-N ball in his hand, with the forearm horizontal (see the figure). He can support the ball in this position because of the flexor muscle force M, which is applied perpendicular to the forearm. The forearm weighs 19.1 N and has a center of gravity as indicated. Find (a) the magnitude of and the (b) magnitude and (c) direction (as a positive angle counterclockwise from horizontal) of the force applied by the upper arm bone to the forearm at the elbow joint. Upper arm bone Flexor muscle Elbow joint 0.330 m (a) Number (b) Number (c) Number Units Units UnitsExplanation / Answer
a) M*0.051 = 19.1 * ( 0.051+0.089) + 171*0.33
M = 1158.9 N
b) Sum of forces = 0
Fbone = M - 19.1 -171 = 968.8 N (direction: downward)
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