A man holds a 183-N ball in his hand, with the forearm horizontal (see the figur

Question

A man holds a 183-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 , which is applied perpendicular to the forearm. The forearm weighs 24.4 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.

I already found (a) and (b), but I cant figure out how to get (c). It needs to be an exact angle measurement in degrees.

(a) 0.330m(183N)+(0.0510m+0.0890m)24.4= 0.0510m*M

So M= 1251.098N

(b) The sum of the forces must equal zero F= 1251.098N-(24.4N + 183N)

F= 1043.698 N

The hint for (c) is just to use trig, but for some reason I cant figure it out.

Explanation / Answer

Part (a) and part (b) are correct.

Part (c), the direction of the force F can be determined as follows:

The magnitude of the force M ( exert by Flexor muscle) is greater than the weight of the ball(W) and weight of the form arm(w).

From the figure, the net force on the system is,

             M = W + w + F

Therefore, the direction of the force F should be in downwards to remains the system in equilibrium.

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.