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Solved: BIO Supporting a Broken Leg. A therapist tells a
Chapter 11, Problem 55P(choose chapter or problem)
BIO Supporting a Broken Leg. A therapist tells a \(74-\mathrm{kg}\) patient with a broken leg that he must have his leg in a cast suspended horizontally. For minimum discomfort, the leg should be supported by a vertical strap attached at the center of mass of the leg–cast system. (Fig. P11.55). In order to comply with these instructions, the patient consults a table of typical mass distributions and finds that both upper legs (thighs) together typically account for 21.5% of body weight and the center of mass of each thigh is \(18.0 \mathrm{~cm}\) from the hip joint. The patient also reads that the two lower legs (including the feet) are 14.0% of body weight, with a center of mass \(69.0 \mathrm{~cm}\) from the hip joint. The cast has a mass of \(5.50 \mathrm{~kg}\), and its center of mass is \(78.0 \mathrm{~cm}\) from the hip joint. How far from the hip joint should the supporting strap be attached to the cast?
Equation Transcription:
Text Transcription:
74-kg
21.5%
18.0 cm
14.0%
69.0 cm
5.50 kg
78.0 cm
Questions & Answers
QUESTION:
BIO Supporting a Broken Leg. A therapist tells a \(74-\mathrm{kg}\) patient with a broken leg that he must have his leg in a cast suspended horizontally. For minimum discomfort, the leg should be supported by a vertical strap attached at the center of mass of the leg–cast system. (Fig. P11.55). In order to comply with these instructions, the patient consults a table of typical mass distributions and finds that both upper legs (thighs) together typically account for 21.5% of body weight and the center of mass of each thigh is \(18.0 \mathrm{~cm}\) from the hip joint. The patient also reads that the two lower legs (including the feet) are 14.0% of body weight, with a center of mass \(69.0 \mathrm{~cm}\) from the hip joint. The cast has a mass of \(5.50 \mathrm{~kg}\), and its center of mass is \(78.0 \mathrm{~cm}\) from the hip joint. How far from the hip joint should the supporting strap be attached to the cast?
Equation Transcription:
Text Transcription:
74-kg
21.5%
18.0 cm
14.0%
69.0 cm
5.50 kg
78.0 cm
ANSWER:
Solution 55P
Introduction
We have to calculate the center of mass of the leg strap system.
Step 1
The mass of one thigh is
And the position of center of mass is