What is the Best Experiment to Illustrify the Law of Universal Gravitation?

[shpotes]

I want to explain the law of universal gravitation but i need an experiment to ilustrate it, any can help me?

What do you think are the best gravity experiment?

 

[UncertaintyAjay]

Jumping off a cliff
Nah, I'm kidding. What exactly do you mean by gravity experiment?

 

[Andrew Mason]

I want to explain the law of universal gravitation but i need an experiment to ilustrate it, any can help me?

In order to show gravity you would have to do something like the Cavendish experiment using a torsion balance with large masses. It is probably best to show a video of the experiment rather than doing it because it is very difficult to set up.

AM

 

[Nugatory]

What do you think are the best gravity experiment?

What do you mean by a "good" experiment? Simple yet profound? An intensely demanding technical effort?

 

[mfb]

I merged two threads.

You can let two things of different mass and shape fall down and compare the time they need. If you have access to a vacuum, you can use a feather and some compact dense object (like a steel ball) to make the experiment better.
The same experiment has been done on the moon - you don't have access to the moon in the classroom, but you can show the video.

 

[UncertaintyAjay]

n order to show gravity you would have to do something like the Cavendish experiment

That is a beautiful experiment. You should definitely check it out

 

[Creator]

I want to explain the law of universal gravitation but i need an experiment to ilustrate it, any can help me?

What do you think are the best gravity experiment?

I kinda like this one:

 

[tony873004]

The gravitational constant G is too small to measure in most school labs. To recreate Cavendish would be too difficult for most high schools or universities.

But you can experimentally derive a maximum value for G.

Two buckets of water, each about 7 kg, 1 meter apart, would take about 9 hours to "fall" to each other if placed on a perfectly friction-free tabletop.

Intuitively the students know this won't happen.

Find the coefficient of static friction between the bucket and the table by inclining the table until the bucket slides. Then measure the slope. (either rise over run or tan of the angle) .

Let's assume it's 0.3.

The force of static friction must be at least as strong as the gravitational force between the buckets, or the buckets will begin to slide towards each other.

Now the competition between the students is to see who can experimentally measure the smallest value. They'll never get close to 6.67e-11. The competition is really who can find the densest objects (so they minimize the distance while maximizing mass) and the smoothest surface (but don't tell them that. Let them figure it out from the formulas). Don't use round objects. They must slide!
$$\begin{array}{l} f_s \ge \frac{{GMm}}{{r^2 }} \\ \mu _{s,\max } mg \ge \frac{{Gmm}}{{r^2 }} \\ \mu _{s,\max } g \ge \frac{{Gm}}{{r^2 }} \\ \frac{{\mu _{s,\max } gr^2 }}{m} \ge \frac{G}{{}} \\ G \le \frac{{\mu _{s,\max } gr^2 }}{m} \\ G \le \frac{{0.3\left( {9.8\,{\rm{m/s}}^{\rm{2}} } \right)\left( {1\,{\rm{m}}} \right)^2 }}{{7\,{\rm{kg}}}} \\ G \le 0.42\,\frac{{{\rm{m}}^{\rm{3}} }}{{{\rm{kg - s}}^{\rm{2}} }} \\ \end{array}$$

 

[mfb]

You can improve that limit by at least one order of magnitude with a mass attached to a string. Probably two orders of magnitude. It will also make the experiment easier because you don't have to measure the sliding angle.
You get several orders of magnitude more if you do a Cavendish-like experiment to derive an upper limit.

We had that experiment in university, and the result was reasonable (~10% uncertainty).

 

[Vanadium 50]

I believe Iowa State has their undergrads measure G. It's much easier than in Cavendish's day, with cameras and lasers available and cheap. It's important to understand how this experiment scales, or rather, how it doesn't. A bigger experiment is no better.

https://www.fourmilab.ch/gravitation/foobar/ has some interesting stuff on home gravity experiments.

 

[Jakecp]

Hello,
Thought i am not an educator but just an eight grade student i want to share me and my team work we did to explain a gravity project. I believe it is worthless doing it if we don't share it.

https://drive.google.com/file/d/0B-91fm1d7JtKbkN3UFY4WlljSWM/view?usp=sharing

Regards!

 

[Jakecp]

And here also a balance experiment.

https://drive.google.com/file/d/0B-91fm1d7JtKN1d0VFpUNjZNVDA/view?usp=sharing

Regards!

 

[whitsona]

I kinda like this one:

I've been looking at this one lately as well. Has anyone done it?

Cavendish had to spend so much time avoiding air currents, etc. that I've been wondering about how feasible it is.

 

[whitsona]

I've been looking at this one lately as well. Has anyone done it?

Cavendish had to spend so much time avoiding air currents, etc. that I've been wondering about how feasible it is.

Oh! Just went to the link that Vanadium 50 posted. The water break seems to be the piece of it that I was missing! Can't wait to try this.