Are work and moment the same thing? They both have the same units

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Discussion Overview

The discussion centers on the relationship between work and moment (torque), exploring their definitions, units, and whether they can be considered the same concept. The scope includes conceptual clarification and technical explanation regarding the nature of these physical quantities.

Discussion Character

  • Conceptual clarification
  • Technical explanation
  • Debate/contested

Main Points Raised

  • Some participants note that both moment and work are expressed in Newtons-meters, leading to confusion about their equivalence.
  • One participant corrects an earlier claim, stating that moment is Newtons-meters and work is also Newtons-meters, but emphasizes that they are not the same due to differences in how force is applied in each case.
  • Another participant raises a question about work done when a force is applied but there is no movement, suggesting that work should equal zero in such a scenario.
  • One participant clarifies that work is defined as force multiplied by distance, indicating that no work is done if there is no movement.
  • There is a discussion about the units of pressure, with some participants correcting each other regarding the proper expression of units.
  • A participant points out that while torque and energy have the same dimensional units, this does not imply they can be treated as the same quantity.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between work and moment, with some asserting they are not the same due to the conditions under which each is defined. The discussion remains unresolved regarding the implications of their similar units.

Contextual Notes

There are limitations in the discussion regarding the assumptions made about the application of force and the definitions of work and moment. The conversation also reflects some confusion about the correct units and their interpretations.

Femme_physics
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Moment is Newtons per meter, and work is Newtons per meter. I'm confused as to how to relate them. Are they essentially the same thing?
 
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Femme_physics said:
Moment is Newtons per meter, and work is Newtons per meter. I'm confused as to how to relate them. Are they essentially the same thing?

Correction : Moment is Newtons-meters, and work is Newtons-meters.

No they're not the same. For work the force has to be in the same direction (vector dot product) as relevant distance (that is the distance traveled), whereas for torque the force has to be perpendicular (vector cross product) to the relevant distance (which is the lever length).
 
Ah I see, thanks uart :)
 
I just thought of something.

If I push on something with 400 NEwtons, and it doesn't move - does work = 0? Or 400 N/m?

Because if I apply a moment on something and it doesn't rotate, I know that the moment is still worth its amount regardless of whether there was or wasn't rotational movement.
 
Work is force x distance. So there is no work done if the object doesn't move.

N/m is a unit of pressure. Work units is Nm.
 
Ah, sorry for repeatedly confusing the units...and thanks for clarifying my suspicion, jarednjames.
 
jarednjames said:
N/m is a unit of pressure. .

Huh? Not N/m^2?
 
Oldfart said:
Huh? Not N/m^2?

Bugger, good catch!
 
Dimensionally, torque (moment) has the same units as energy. However, that alone does not give you permission to add these totally different quantities.
 

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