Direction of Torque: Understanding the Basics

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Discussion Overview

The discussion revolves around the concept of torque, specifically its direction and how it is represented. Participants explore the relationship between torque's direction and its representation as an axial vector, as well as the implications of using clockwise or counterclockwise terminology.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asserts that when applying force to a wrench, the torque should also be considered to rotate in the same direction (clockwise).
  • Another participant suggests that while using clockwise or counterclockwise descriptions can be acceptable, it is limited by the observer's perspective and that using an axial vector is more robust.
  • Participants discuss the right hand rule as a method to interpret torque direction, noting that torque along the +ve z axis corresponds to a counterclockwise rotation when viewed from a specific perspective.
  • There is a question about whether understanding torque as a cross product of position and force vectors is necessary for interpreting its direction, with differing opinions on this point.
  • One participant expresses confusion about not being able to view part of another's post, indicating potential technical issues in the thread.

Areas of Agreement / Disagreement

Participants express differing views on the necessity of understanding torque as a cross product for interpreting its direction, indicating that the discussion remains unresolved on this point.

Contextual Notes

Participants reference the right hand rule and axial vector representation, but the discussion does not fully resolve the implications of these concepts for understanding torque direction.

Amar.alchemy
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Hi,

Let us assume that I apply some amount of force at the end of the wrench to loosen a nut. This force makes the wrench to rotate in clockwise direction. So the direction of the torque should also be in clockwise direction.
However, we usually use the definition of cross product to determine the direction of Torque ie if both position vector and Force vector are in the xy plane then the direction of Torque will be either +ve z-axis or -ve axis depending upon the rotation of the body.
My confusion is why can't we say the direction of the torque is in clockwise direction or counter clockwise direction?? What exactly it means if we say the direction of the torque is along +ve z axis or -ve z axis??
 
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Amar.alchemy said:
My confusion is why can't we say the direction of the torque is in clockwise direction or counter clockwise direction??
For some purposes, it's perfectly OK to describe the torque as clockwise or counterclockwise. But what if you were looking at the wrench from the other side? Describing torque using an axial vector is more robust.
What exactly it means if we say the direction of the torque is along +ve z axis or -ve z axis??
Use the right hand rule to interpret the direction of the torque. If the torque is along the +ve z axis, that means that looking down (towards the -ve z direction) the torque would be counterclockwise.

See: http://hyperphysics.phy-astr.gsu.edu/HBASE/tord.html"
 
Last edited by a moderator:
Doc Al said:
For some purposes, it's perfectly OK to describe the torque as clockwise or counterclockwise. But what if you were looking at the wrench from the other side? Describing torque using an axial vector is more robust.

Use the right hand rule to interpret the direction of the torque. If the torque is along the +ve z axis, that means that looking down (towards the -ve z direction) the torque would be counterclockwise.

So when i say someone that the direction of torque is along the +ve z axis then it is necessary for him to know that torque is a cross product of positon vector and Force vector otherwise he can't tell whether it is clockwise or counter clockwise. Is my understanding correct??

And one more thing, in the thread I'm not able to view second paragragh of ur post, i saw it when i clicked "quote" button...
 
Amar.alchemy said:
So when i say someone that the direction of torque is along the +ve z axis then it is necessary for him to know that torque is a cross product of positon vector and Force vector otherwise he can't tell whether it is clockwise or counter clockwise. Is my understanding correct??
No, all they have to know is the right hand rule convention for defining torque. (See the link in my last post.)

And one more thing, in the thread I'm not able to view second paragragh of ur post, i saw it when i clicked "quote" button...
That's probably because I was editing it while you were responding. You should be able to see it now.
 
ya, Thanks i got it :smile:
 

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