The bones of the forearm (radius and ulna) are hinged to the humerus at the elbo

Question

The bones of the forearm (radius and ulna) are hinged to the humerus at the elbow. The biceps muscle connects to the bones of the forearm about 2 cm beyond the joint. Elbow Hand Muscle Assume the forearm has a mass of 2 kg and a length of 0.4 m. When the humerus and the biceps are nearly vertical and the forearm is horizontal. If a person wishes to hold an object of mass M so that her forearm remains motionless, what is the mathematical expression relating the force exerted by the biceps muscle and the mass M? Now suppose that instead of a mass, you want to hold a cable in this position. You grip the handle of the cable and pull it up until your forearm is horizontal and the cable makes an angle of 30 degrees with the horizontal. Find a mathematical expression for the force exerted by the biceps muscle as a function of the tension T in the cable. Briefly state three approximations or assumptions that you made in your solution(s) above.

Explanation / Answer

F = force by the muscle

F x 0.02 = M x .4

F = 20 M

case 2

F x .02 = Tsin30 x .4

F = 10T

assumptions

the bicep muscle are acting vertically

the distance of the acting of the force remains constant at all times

no other muscle comes into picture as far as application of force is concerned

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