alleryStart learning →A biceps muscle exerts 470 N to hold a forearm and a book whose combined weight is 63.7 N. What is the ratio of muscle force to weight supported?
A7.38
B0.136
C6.38
D1.14
Answer & Solution
Correct answer: A. 7.38
1. The ratio wanted is the muscle force divided by the weight it supports.
2. Substituting, 470 N / 63.7 N = 7.38.
3. The muscle therefore pulls with more than seven times the weight it holds up.
4. This large factor follows from the mechanical advantage of the arm being far below one.
5. The value 6.38 is the corresponding ratio for the elbow joint force, not the muscle force.
_Source: OpenStax College Physics (CC BY 4.0), Ch 9 "Statics and Torque", section 9.6 Forces and Torques in Muscles and Joints_
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