A standard bowling ball weighs 17 pounds. You wish to hold a bowling ball in fro

Question

A standard bowling ball weighs 17 pounds. You wish to hold a bowling ball in front of you, with the elbow bent at a right angle. Assume that your biceps attaches to your forearm at 2.5 cm out from the elbow joint, and that your biceps muscle pulls vertically upward, that is, it acts at right angles to the forearm. Also assume that the ball is held 38 cm out from the elbow joint. Let the mass of your forearm be 5.4 kg and assume its center of gravity is located 19 cm out from the elbow joint. How much force must your biceps muscle apply to forearm in order to hold out the bowling ball at the desired angle?

Explanation / Answer

Since all the forces are normal to the elbow, we can balance the torque at the elbow joint to find the required force of the biceps (F N) as:

F* 0.025 = (7.7* 9.8* 0.38) + (5.4* 9.8* 0.19) [17 pounds= 7.7 kg approx.]

Therefore, F= 1549 N (approx.)

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