Physics Science Research Idea

[yuuma]

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 differnt forces, and they dont 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.

[deleted-71709]

Hello yuuma,

I must admit I'm not quite clear on what you propose to do in your experiment. As I see it, you desire to measure gravitational forces between two relatively small masses by measuring motion. This is certainly a novel idea.

I see you are planning to do these measurements inside a box. I presume this is to eliminate the effects of air currents and such? This would be a good first step.

First, you need to learn about Newton's law of universal gravitation. With that, you can estimate the gravitational force that will exist between the masses you plan to use. You will discover these forces are incredibly small. Of course, even incredibly small forces can cause motion when applied to any size mass. That's what Newton's second law of motion will tell you. The motion will be incredibly small, unless the mass of the object is near zero.

You can see that what you are trying to measure will be extremely difficult, unless, of course, I do not understand your experiment correctly.

I suggest you study Newton's laws, do some simple calculations, and determine for yourself if what you propose is doable.

Good luck.

[yuuma]

Hi, thank you for the reply!

Yes, I am trying to measure the gravitational force of two small masses.
The box is to prevent any air currents from disturbing the experiment.
To get a more exact result, I was thinking of putting a mirror on the balance so
when I shoot a laser at it, I can figure out the angle it rotated. I will compare the initial distance to where it is
after every hour during the experiment, and see if it speeds up in a linear function or an expodential function as
the masses move closer. I believe this is a far more accurate
way to measure the distance.

I am currently enrolled in Physics B AP, and I just took a test on Newton's three laws so I am familiar to
his laws to some extent.
-yuuma

[deleted-71495]

What you're proposing sounds like a torsion balance setup commonly known as the Cavendish experiment. I actually remember doing this in physics lab, long ago. The wikipedia article on it is a good starting point: http://en.wikipedia.org/wiki/Cavendish_experiment. Using a laser/mirror setup to measure the torsion angle is a good idea, I think the key will be to find the suitable materials for it so you get consistent results.
Since the experiment as such is not really original, perhaps you can modify your idea into a study of materials to use for obtaining the best trade-off of range and accuracy?