Can Gravity Be Manipulated in a Science Fair Project?

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Discussion Overview

The discussion revolves around the feasibility and originality of a science fair project aimed at measuring the gravitational effect between two masses. Participants explore the theoretical framework, practical challenges, and potential modifications to enhance the project.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Homework-related

Main Points Raised

  • One participant proposes an experiment involving two lead masses and a suspended bar to measure gravitational effects, questioning its originality and feasibility.
  • Another participant expresses skepticism about the practicality of the experiment without advanced measuring equipment, suggesting it may not be unique.
  • A third participant references the Cavendish experiment, noting the challenges of measuring small gravitational forces and the presence of opposing forces like friction and air resistance.
  • One participant acknowledges the difficulty of constructing the necessary apparatus but suggests seeking access to existing equipment at educational institutions.
  • Another participant shares their experience with a simpler project using a pendulum to measure gravitational acceleration, indicating an alternative approach to the same concept.
  • Some participants discuss the possibility of building a home-made version of the apparatus, while questioning the safety of using lead.
  • One participant finds a resource indicating that home experiments are possible, seeking information about the availability of the required instruments at colleges in the Los Angeles area.

Areas of Agreement / Disagreement

Participants express a mix of skepticism and encouragement regarding the feasibility of the proposed experiment. There is no consensus on the originality or practicality of the project, and multiple competing views about the challenges and alternatives remain present.

Contextual Notes

Participants highlight limitations such as the need for high accuracy in measurements, the impact of external forces, and the potential difficulty in constructing the apparatus. These factors contribute to the uncertainty surrounding the project's execution.

Who May Find This Useful

Students interested in physics experiments, educators looking for project ideas, and individuals exploring gravitational measurement techniques may find this discussion relevant.

kakashi1027
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Hi,

I am currently thinking of a topic for my science fair project, and I was thinking about calculating the effect of gravity between two masses. The first mass(most likely lead or some other dense material) will be taped/glued to an bar with minimal mass, such as styrofoam or thin plastic so it will have minimal effect on the result. The bar will then be suspended from the roof of an box with a string. Then two pieces of lead far bigger than the ones suspended will be placed at the same height at a specific distance from the bar.


Theoretically, the x-forces and the y-forces are two different forces, and they don't affect each other, so Earth's gravity shouldn't affect this experiment at all. To remove the constant motion caused after the initial gravitational force, a dampener will be placed, which will most likely be a pad dipped in water to dampen the motion so only gravity affects it.


The independent variables will most likely be the density of the two masses, the ratio of the two masses, and the distance between the masses. The dependent variables will be the speed the first mass moves.


I would like to know if 1. if this is even possible, 2. if i should change some features to make it more interesting, and 3. If this overall would be a good experiment and is it original. i must do a project which is new and has not been done before.
 
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I hate to come across as being a wet blanket, but I don't think that such an experiment can be undertaken with anything less than multi-million dollar measuring equipment. I don't know that you could call it "unique", but it certainly isn't done on a daily basis. If you can pull it off on a budget, it'll be a show-stopper.
 
This is a known old experiment for measuring G. I have seen the instrument at my college.

check http://en.wikipedia.org/wiki/Cavendish_experiment

However it is difficult to perform properly, because gravitation forces are so small.
You have made a mistake with the assumption that there would be no forces opposing movement (appart from force of dampener). First there will be friction forces and air resistance and secondly the string will resist torsion with a tiny torque, since a torsion requires stretching of the outside layers. This torque is most usefull for measuring force because it is independent of speed, so you can calculate force from the equilibrium distance to which the suspended mases move. This is basicaly a weighing machine with very small
friction and very small force/displacement quotient.

You certainly won't be able to construct this instrument yourself, because the required accuracy is too high. However you could find a school/colledge that has this apparatus and ask if they permit you to make a measurement.
 
I stand corrected. Thanks for the info, Lojzek. I honestly didn't think that anything so simple could measure something to that degree of accuracy.
 
Hi, thanks for the replys.
If I were to get in hold of the instrument, is there anything that I can change to make this project "stand out" from other projects?
thanks!
 
kakashi1027 said:
If I were to get in hold of the instrument, is there anything that I can change to make this project "stand out" from other projects?
thanks!

That you'd even be able to pull it off would be quite a feat.
 
Apparently it is possible, though difficult, to build a home-brew version. http://www.sas.org/tcs/weeklyIssues_2005/2005-07-01/feature1/index.html

I'm not sure what one could reasonable substitute for the toxic lead.
 
Last edited by a moderator:
I did a similar project in school.

We used a pendulum and measured it's period. Once we had that we could use it to calculate g.

We could then 'prove' the mass of the Earth to show our measured value is correct.

Not quite the same, but along the same lines and far simpler to do. Same end result.
 
Hi, I found another project done at home, so its not "impossible" to do at home.
http://www.fourmilab.ch/gravitation/foobar/

and I was wondering if that instrument Lojzek was talking about is common among colleges, and if there are any colleges in the Los Angeles area with that instrument.
Thanks again!
 

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