Greatest Lever Arm: Calculating Force at Elbow Joint

In summary, the conversation is about determining the lever arm in a diagram and understanding where the force is coming from and where it is pointing. The lever arm is the perpendicular distance from the fulcrum to the line of action of the force. The question may be asking for the lever arm of the force of the weight held in the hand.
  • #1
NA19
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Homework Statement


The diagram is attached. It is asking which position has the greatest lever arm.

Homework Equations


The Attempt at a Solution


So, I know that the elbow is the fulcrum but what I'm struggling with is how to draw the force arrow. Where is the force coming from and where is it pointing? What is a good way to know where to draw the lever arm?
 

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  • #2
The force comes from the contracting muscle. So look at the direction in which the connecting tissue from the muscle connects to the bone. The force will pull along this direction on the forearm. The lever arm is then the perpendicular distance to this direction.
 
  • #3
So is the lever arm the forearm?
 
  • #4
No. It is the perpendicular distance dropped from the fulcrum onto the line of action of the force.
 
  • #5
So are the black lines that I drew correct for the line of force?
And the red for the lever arms?
 

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  • #6
The question should actually state explicitly for which force the lever arm is required. There are several forces in this diagram, but I am getting the impression its wants you to get the lever arm of the force of the weight held in the hand. The weight F acts downwards along the pink line in the first diagram and its lever arm is the orange L. If the lever arm of the force that the muscle is exerting on the forearm were required it would be the much shorter L in the second diagram.
 

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Last edited:

1. What is a lever arm and how does it relate to calculating force at the elbow joint?

A lever arm is the distance between the point of rotation and the point where force is applied. In the case of the elbow joint, the lever arm is the distance between the elbow joint and the point where the muscle attaches to the bone. This distance is used in the calculation of force at the elbow joint.

2. How is the force at the elbow joint calculated using the lever arm?

The force at the elbow joint can be calculated using the equation F = d x F, where F is the force applied, d is the length of the lever arm, and F is the force produced at the elbow joint. This equation is based on the principle of torque, which states that the force applied to an object is equal to the product of the distance from the point of rotation and the force applied.

3. How does the length of the lever arm affect the force at the elbow joint?

The longer the lever arm, the greater the force at the elbow joint will be. This is because a longer lever arm allows for a greater torque to be applied, resulting in a greater force being produced at the elbow joint.

4. What other factors besides the lever arm can affect the force at the elbow joint?

The force at the elbow joint can also be affected by the angle at which the force is applied and the strength and size of the muscles involved. The type of movement being performed, such as flexion or extension, can also impact the force at the elbow joint.

5. How can understanding the concept of lever arm and calculating force at the elbow joint be useful in daily life?

Understanding the concept of lever arm and calculating force at the elbow joint can be useful in a variety of activities, such as weightlifting, sports, and even household chores. By understanding how to apply force efficiently, individuals can minimize the risk of injury and maximize their strength and performance in various tasks.

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