Question

Suppose the biceps were surgically reattached three centimeters farther toward the person's hand. If the same bowling ball were again held in the person's hand, how would the force required for the biceps be affected? Explain? (Select all that apply.) It would require less force because of the larger distance between the elbow and the location where the force from the biceps acts. It would require more force because the force is less nearly perpendicular to the moment arm. It would require more force because of the larger distance between the elbow and the location where the force from the biceps acts. It would require more force because the force acts closer to the heavy bowling ball. It would require less force because the torque for each newton of force from the biceps is greater. PRACTICE IT Use the worked example above to help you solve this problem. A W = 52.8 N (11.9 lb) weight is held in a person's hand with the forearm horizontal, as shown in the figure. The biceps muscle is attached d = 0.03039 m from the joint, and the weight is l = 0.353 m from the joint. Find the upward force vector F exerted by the biceps on the forearm (the ulna) and the downward force vector R exerted by the humerus on the forearm, acting at the joint. Neglect the weight of the forearm. F = N R = N EXERCISE HINTS: GETTING STARTED | I'M STUCK! Use the values from PRACTICE IT to help you work this exercise. Suppose you wanted to limit the force acting on your joint to a maximum value of 8.13 102 N. (a) Under these circumstances, what maximum weight would you attempt to lift? N (b) What force would your biceps apply while lifting this weight? N

Answer 1

As the distance from bicep force to elbow joint is increasing,

It would require less force because of the larger distance between the elbow and the location where the force from the biceps acts

It would require less force because the torque for each newton of force from the biceps is greater.

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Practice it:

Weight held in hand is ( downward) is acting at a distance of from the elbow joint.

Bicep force ( upward) is acting at a distance of from the elbow joint.

A downward force is acting at the elblow joint.

Net torque on the forearm about the elbow joint is zero,

Upward force exerted by the biceps on the forearm is

Net force acting on forearm is zero,  

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Practice it:

Limiting value of force acting on the joint is

a)

Net Torque on the forearm about the biceps is zero,

Maximum weight that can be lifted is

b)

Net force acting on forearm is zero,

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