Torque is same all along lever?

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    Lever Torque
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Discussion Overview

The discussion revolves around the concept of torque in the context of a lever system, specifically regarding how torque relates to force and lever arm length. Participants explore the mathematical definition of torque, its conceptual implications, and the conditions required for equilibrium in a lever system.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion about the relationship between torque and force, initially believing that torque should increase as the lever arm decreases.
  • Another participant clarifies that torque is defined as the product of force and distance from the pivot point (F*d), indicating that as the distance decreases, the torque must also decrease.
  • A different participant challenges the idea that torque is the same along the lever, stating that torque is only defined about a pivot point and must be equal for the system to be in equilibrium.
  • One participant reflects on their understanding, realizing that the downward force of the ball requires an upward force from the forearm, leading to equal torques about the pivot.

Areas of Agreement / Disagreement

Participants do not reach a consensus on whether torque is the same everywhere along the lever, with some asserting it is not the case while others seem to misunderstand this aspect. The discussion remains unresolved regarding a clear conceptual understanding of torque.

Contextual Notes

There are limitations in the participants' understanding of torque, particularly regarding its definition and application in different contexts. The discussion reveals a dependency on the pivot point for defining torque and the conditions necessary for equilibrium.

yosimba2000
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Here's my background so you know where I'm having trouble. I've attached a picture.

I have to find the force produced by the muscle to keep the arm and ball at its current position in the picture. Now, I originally assumed Torque was Force in rotation, and intuitively thought you would need to use more force if you're closer to the pivot (shorter lever arm) than compared to the end (longer lever arm). I was right about force needed being greater as the lever arm got shorter, but I'm having touble understanding why the Torque along the lever must be the same. So, now I know Torque and Force are not the same.
Mathematically, I know there's only one right answer, but how about conceptually? What is torque if it's not force? What does it represent? Why isn't the torque increasing as the lever arm length decreases?

Thanks!
 

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Torque is the perpendicular force times the distance to the pivot point. It is completely different from force. it is F*d.
Given that, you can see that as d decreases, so does the torque.

In this case, in order to hold the weight steady, the two torques must be equal. Because d for the muscle is much less than the other, it requires a much larger force.

does that help?
 
Last edited:
sorry, it still hasn't clicked. I mean, mathematically I agree with what you've said, but I still can't understand what Torque represents. What is it that makes it the same everywhere along the lever?
 
it is not the same everywhere along the lever. torque is only defined about a pivot point. For the arm to hold the weight steady, the two torques about that point must be equal.

I am at a loss for offering an easy conceptual understanding. I just think of it as F*d.
 
wait I think I've got it now. I was originally thinking of the upward force that the forearm would provide to support the ball, but now I'm thinking of the ball dragging down the forearm. And to balance that we need an upward force and the torques have to equal. Thanks a bunch!
 
you're welcome :)
 

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