A 60-Kg Ball Is Held in the Hand with the Lower

question 31

Multiple Choice

A 6.0-kg ball is held in the hand with the lower arm making a 90-degree angle with the upper arm. The lower arm and hand have a combined mass of 2.5 kg and a center of mass 18 cm from the elbow joint. The ball is 40 cm from the elbow joint. If the biceps muscle is 12 cm from the center-of-mass point of the lower arm and hand, calculate the force that the biceps muscle must exert in order to keep the lower arm and hand horizontal.

• A) 466 N
• B) 48.0 N
• C) 392 N
• D) 233 N
• E) none of the above

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