Leigh 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 dumbbell 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.

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Leigh 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 dumbbell 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.

The image depicts a leg bent at the knee with a weight attached to the ankle. The upper leg is positioned horizontally, while the lower leg is angled downward. Two distance measurements are indicated with arrows and labels: 

1. The horizontal distance from the knee to the ankle is labeled as "30 cm."
2. The vertical distance from the knee to the foot is labeled as "40 cm."

This diagram is likely used in an educational context to illustrate principles of biomechanics or physics, such as torque or lever systems, by demonstrating the impact of weights and positioning on joint movement.
Transcribed Image Text:The image depicts a leg bent at the knee with a weight attached to the ankle. The upper leg is positioned horizontally, while the lower leg is angled downward. Two distance measurements are indicated with arrows and labels: 1. The horizontal distance from the knee to the ankle is labeled as "30 cm." 2. The vertical distance from the knee to the foot is labeled as "40 cm." This diagram is likely used in an educational context to illustrate principles of biomechanics or physics, such as torque or lever systems, by demonstrating the impact of weights and positioning on joint movement.
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Why must the torque due to the weight be equal in magnitude?

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