A man holds a 198-N ball in his hand, with the forearm horizontal (see the figure). He can support the ball in this position because of the flexor muscle force line M , which is applied perpendicular to the forearm. The forearm weighs 24.4 N and has a center of gravity as indicated. Find (a) the magnitude of line M and the (b) magnitude and (c) direction (as a positive angle counterclockwise from horizontal) of the force applied by the upper arm bone to the forearm at the elbow joint.

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A man holds a 198-N ball in his hand, with the forearm horizontal (see the figure). He can support the ball in this position because of the flexor muscle force line M , which is applied perpendicular to the forearm. The forearm weighs 24.4 N and has a center of gravity as indicated. Find (a) the magnitude of line M and the (b) magnitude and (c) direction (as a positive angle counterclockwise from horizontal) of the force applied by the upper arm bone to the forearm at the elbow joint.

The image depicts the anatomy and mechanics of the human arm during a flexion movement involving the flexor muscle. Key components and measurements are illustrated as follows:

1. **Upper Arm Bone**: The upper section of the arm, which is attached to the shoulder.
   
2. **Elbow Joint**: The pivot point of the arm, displayed near the intersection of the upper arm bone and forearm.

3. **Flexor Muscle**: Highlighted in red, this muscle is responsible for bending the arm at the elbow.

4. **Blue Arrow (M)**: Represents the force exerted by the flexor muscle during contraction.

5. **cg (Center of Gravity)**: Located on the forearm, indicating the center of mass for the forearm and hand.

6. **Distances**:
   - From the elbow joint to the force applied by the muscle (M): \(0.0510 \, \text{m}\).
   - From the elbow joint to the center of gravity (cg): \(0.0890 \, \text{m}\).
   - From the elbow joint to the hand holding a ball: \(0.330 \, \text{m}\).

The image illustrates how muscle force and lever arm mechanics interact in the human body to facilitate movement, providing a detailed breakdown of the biomechanical principles involved in arm flexion.
Transcribed Image Text:The image depicts the anatomy and mechanics of the human arm during a flexion movement involving the flexor muscle. Key components and measurements are illustrated as follows: 1. **Upper Arm Bone**: The upper section of the arm, which is attached to the shoulder. 2. **Elbow Joint**: The pivot point of the arm, displayed near the intersection of the upper arm bone and forearm. 3. **Flexor Muscle**: Highlighted in red, this muscle is responsible for bending the arm at the elbow. 4. **Blue Arrow (M)**: Represents the force exerted by the flexor muscle during contraction. 5. **cg (Center of Gravity)**: Located on the forearm, indicating the center of mass for the forearm and hand. 6. **Distances**: - From the elbow joint to the force applied by the muscle (M): \(0.0510 \, \text{m}\). - From the elbow joint to the center of gravity (cg): \(0.0890 \, \text{m}\). - From the elbow joint to the hand holding a ball: \(0.330 \, \text{m}\). The image illustrates how muscle force and lever arm mechanics interact in the human body to facilitate movement, providing a detailed breakdown of the biomechanical principles involved in arm flexion.
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