Finding Mass of Object without Scale

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Discussion Overview

The discussion revolves around methods to determine the mass of an aluminum rod without using a scale. Participants explore various approaches, including theoretical calculations based on dimensions and density, as well as experimental methods involving forces.

Discussion Character

  • Homework-related
  • Exploratory
  • Technical explanation

Main Points Raised

  • One participant seeks assistance in finding the mass of an aluminum rod, indicating they have the dimensions but lack the necessary equations.
  • Another participant suggests that knowing the volume and density of the rod could be essential for solving the problem, and mentions the potential shape of the rod as a circular cylinder.
  • A different approach is proposed, where a participant suggests using a constant force to accelerate the rod and then applying the formula \( F = ma \) to find the mass, though they acknowledge the practical difficulties of this method in a school lab setting.
  • Concerns are raised about how to calculate the force used for acceleration, with one participant noting that a scale might still be necessary.
  • Further elaboration on methods includes using Coulomb's law if charges are involved or applying Hooke's Law if a spring is used, although one participant expresses uncertainty about the name of the spring law.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the best method to determine the mass without a scale, with multiple competing approaches and uncertainties expressed regarding the feasibility of each method.

Contextual Notes

Participants mention various assumptions, such as the shape of the rod and the need for additional measurements (like force), which may affect the proposed methods. There is also a lack of clarity on how to implement the suggested experimental approaches without a scale.

SirSpanky0
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I need to find the mass of an aluminum rod without the use of a scale. I have all the dimensions of the rod but I just don't know the right equations etc. Thanks for the help!
 
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This sounds like it might be a homework problem. Perhaps you know the volume of the rod, and its density?

Maybe you're stuck finding the volume of a "rod". A "rod" could have a lot of shapes, though the first one that springs to mind is that of a circular cylinder.

I think that if this is a homework problem you'd do better if you made some effort to solve it yourself, first (the "show your work" rule) - also, there is a special forum for homework problems.
 
SirSpanky0 said:
I need to find the mass of an aluminum rod without the use of a scale. I have all the dimensions of the rod but I just don't know the right equations etc. Thanks for the help!
You can accelerate it with a constant force and then divide the force exerted and the acceleration and that will give you the mass. Easy to say, hard to do for a lab experiment in school.

Pete
 
pmb_phy said:
You can accelerate it with a constant force and then divide the force exerted and the acceleration and that will give you the mass. Easy to say, hard to do for a lab experiment in school.

Pete

Yes, but how are you going to calculate the force with which you accelerate? you may still need a scale.
 
amt said:
Yes, but how are you going to calculate the force with which you accelerate? you may still need a scale.
It depends on the particular way you choose to accelerate it. If you use two charges then you use Coulombs law. If you use a spring then you use the law for springs (the name evades me at the moment).

Pete
 
pmb_phy said:
[...]If you use a spring then you use the law for springs (the name evades me at the moment).

Would this be Hooke's Law ([itex]F = kx[/itex])? Sorry if I'm wrong, I just like to think I know what's going on once in a while :-p
 
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