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The biceps brachii is the typical muscle we associate with forearm curls. The forearm pivots about the elbow joint and the biceps muscle inserts along the radius (one of two major forearm bones), d₁ = 5 cm from the pivot. In our case, consider a forearm of length of d3 = 34 cm and weight of W = 3lbs, with a center of mass shifted toward the pivot, at d₂ = 15 cm from the elbow. There is a reaction force R at the elbow joint not shown in the figure. As a first approximation, assume the biceps muscle inserts at a 90 degree angle while the forearm is held parallel to the ground. Assume all quantities are correct to 2 significant figures.

The biceps brachii is the typical muscle we associate with forearm curls. The forearm pivots about the elbow joint and the biceps muscle inserts along the radius (one of two major forearm bones), d₁ = 5 cm from the pivot. In our case, consider a forearm of length of d3 = 34 cm and weight of W = 3lbs, with a center of mass shifted toward the pivot, at d₂ = 15 cm from the elbow. There is a reaction force R at the elbow joint not shown in the figure. As a first approximation, assume the biceps muscle inserts at a 90 degree angle while the forearm is held parallel to the ground. Assume all quantities are correct to 2 significant figures.

Elements Of Electromagnetics
Elements Of Electromagnetics
7th Edition
ISBN:9780190698614
Author:Sadiku, Matthew N. O.
Publisher:Sadiku, Matthew N. O.
ChapterMA: Math Assessment
Section: Chapter Questions
Problem 1.1MA
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The biceps brachii is the typical muscle we associate with forearm curls. The forearm pivots about the elbow joint and the biceps muscle inserts along the radius (one of two major forearm bones), d₁ = 5 cm from the pivot. In our case, consider a forearm of length of d3 = 34 cm and weight of W 3lbs, with a center of mass shifted toward the pivot, at d₂ = 15 cm from the elbow. There is a reaction force R at the elbow joint not shown in the figure. As a first approximation, assume the biceps muscle inserts at a 90 degree angle while the forearm is held parallel to the ground. Assume all quantities are correct to 2 significant figures. M d₂ W d3 F
Transcribed Image Text:The biceps brachii is the typical muscle we associate with forearm curls. The forearm pivots about the elbow joint and the biceps muscle inserts along the radius (one of two major forearm bones), d₁ = 5 cm from the pivot. In our case, consider a forearm of length of d3 = 34 cm and weight of W 3lbs, with a center of mass shifted toward the pivot, at d₂ = 15 cm from the elbow. There is a reaction force R at the elbow joint not shown in the figure. As a first approximation, assume the biceps muscle inserts at a 90 degree angle while the forearm is held parallel to the ground. Assume all quantities are correct to 2 significant figures. M d₂ W d3 F
a) If the person described above is holding a 24 lb object exerting a force F in static equilibrium, what is known about the tension force M applied by the biceps brachii? b) cal En The force is less than 24 lbs. The force is equal to 24 lbs. The force is greater than 24 lbs but less than 27 lbs. The force is equal to 27 lbs. The force is greater than 27 lbs. M = IOS e conditions of static equilibrium, rachii. c) Using the numerical values stated in the problem, your answer for (b), and the conditions of static equilibrium, calculate the magnitude of the reaction force R in lbs, produced at the elbow joint. Enter to 2 significant figures R = lbs d) In what direction is the reaction force that you calculated in part c? e) The forearm is lowered from horizontal. The biceps brachii now meets the radial arm at an angle of 60 degrees rather than 90 degrees. How does this effect the magnitude of the tension force M compared to the horizontal arm orientation? Hint: It might be helpful to refer to torque equilibrium for this case. What happens to the moment arm of all forces?
Transcribed Image Text:a) If the person described above is holding a 24 lb object exerting a force F in static equilibrium, what is known about the tension force M applied by the biceps brachii? b) cal En The force is less than 24 lbs. The force is equal to 24 lbs. The force is greater than 24 lbs but less than 27 lbs. The force is equal to 27 lbs. The force is greater than 27 lbs. M = IOS e conditions of static equilibrium, rachii. c) Using the numerical values stated in the problem, your answer for (b), and the conditions of static equilibrium, calculate the magnitude of the reaction force R in lbs, produced at the elbow joint. Enter to 2 significant figures R = lbs d) In what direction is the reaction force that you calculated in part c? e) The forearm is lowered from horizontal. The biceps brachii now meets the radial arm at an angle of 60 degrees rather than 90 degrees. How does this effect the magnitude of the tension force M compared to the horizontal arm orientation? Hint: It might be helpful to refer to torque equilibrium for this case. What happens to the moment arm of all forces?
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