For this position, what torque is created by the weight about her knee joint axis? b. If the moment arm of the knee extensor muscles is 4 cm about the knee joint axis, what amount of force must these muscles produce to hold the leg in the position described
For this position, what torque is created by the weight about her knee joint axis? b. If the moment arm of the knee extensor muscles is 4 cm about the knee joint axis, what amount of force must these muscles produce to hold the leg in the position described
College Physics
11th Edition
ISBN:9781305952300
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
Chapter8: Rotational Equilibrium And Dynamics
Section: Chapter Questions
Problem 88AP
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Question
Amaris is doing a knee extension exercise using a 100 N weight strapped to her ankle 40 cm from her knee joint. She holds her leg so that the horizontal distance from her knee joint to the weight is 30 cm.
a. For this position, what torque is created by the weight about her knee joint axis?
b. If the moment arm of the knee extensor muscles is 4 cm about the knee joint axis, what amount of force must these muscles produce to hold the leg in the position described? Ignore the weight of the leg.
Expert Solution
Step 1
a) force = 100 N.
Distance of force line from axis = 30 cm
= 0.3 m
So, moment = 100 ×0.3= 30 N.m
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