Mechanical Advantage vs. Lever vs. Human Error

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Discussion Overview

The discussion focuses on the concepts of Mechanical Advantage (MA) and lever mechanics, specifically regarding first-class levers. Participants explore the implications of gravitational constants on calculations of lever ratios and mechanical advantage in different contexts.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant presents calculations for mechanical advantage and lever ratios, questioning the relevance of gravitational constants in these calculations.
  • Another participant asserts that mechanical advantage remains constant regardless of the gravitational context, indicating that the same lever ratio applies on different planets.
  • A third participant reinforces the idea that the weights involved are already expressed as forces, thus negating the need to factor in gravitational acceleration again.

Areas of Agreement / Disagreement

Participants generally agree that gravitational constants do not affect the mechanical advantage in lever calculations, but there is a lack of consensus on the initial understanding of how these concepts interrelate.

Contextual Notes

Participants express varying interpretations of the role of gravitational constants in mechanical advantage calculations, highlighting potential misunderstandings about force and weight definitions.

BMR
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This is my first post here, so pardon if forum guidelines/criteria require this to be designated elsewhere.

I am designing a clamp mechanism utilizing lever mechanics, and I am getting conflicting info regarding Mechanical Advantage and the Law of 1st Class Levers. Regarding MA, knowing that
300px-Lever_mechanical_advantage.png

e4516522ccaaa831010fc757760110894929d202


If:
FB = 40,000 lbs
FA = 1,000 lbs
Then: b = 40, a = 1, and the MA is 40:1

In regards to Levers (Specifically 1st Class Levers)
torque_lever.png

F2 = F1 L1 / L2

If:
FB = 40,000 lbs
FA = 1,000 lbs

Then:
40,000 = 1,000 (32.174 ft/s2 [gravity constant]) (L1 / L2)
40 = 32.174 (L1 / L2)
L1 / L2 = approx. 1.243 or 1.243:1.

So for 1,000 lbs to lift 40,000 lbs., either a 40:1 or 1.243:1 lever ratio is required. Am I simply wrong for factoring in a gravitational constant?
 

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BMR said:
Am I simply wrong for factoring in a gravitational constant?
Yes. You get the same mechanical advantage whether the lever is on the Earth, the Moon or in free space.

On Edit: Assuming that F1 and F2 are either both pushing forces or both weights, that is.
 
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BMR said:
So for 1,000 lbs to lift 40,000 lbs., either a 40:1 or 1.243:1 lever ratio is required.

@kuruman gave you the correct answer. But to amplify, if you move the whole apparatus to a planet with one half Earth's gravity, then the same weights would weigh 500 lbs and 20000 lbs, but the ratio 40:1 remains unchanged and the MA remains unchanged. That is why you don't need G.
 
Another way to say the same thing as @anorlunda: If the number 1000 is a mass, then you multiply by g to get a weight which is a force. Here you have 1000 lbs which is already a force (the mass has already been multiplied by g) so it would be wrong to multiply by g again.
 
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