I need same size balls different mass HEEELP!!!

McLS

McLS

Active member
I don't know if anyone can help out but here we go:

I need (for a trampoline math/physics applied project) balls (spheres) of the exact same size (ranging from 10cm diameter up to a metre) but with different masses: Ideally i'd need a set of balls of same radius with 1kg, 2kg, 3kg, 5....10kg. Although 5 different masses (but proportional, like 4, 6, 8, 10) would be fine, i need 4 different masses at least.

I've looked into medicinal sport balls, but can only find 2 different masses for same size...they evidently get bigger as they get heavier.

I also thought of filling a same size football with different materials, but that would get me 3 different weights max.

I need the minimum weight to be 500g or else it won't bounce on the tramp.

PLEASE PLEASE PLEASE help me out here, im going crazy...
 
13188914:stucci said:
why don't you get an exercise ball and fill it with differing amounts of sand?
Click to expand...

thought about it but i need the masses to be of 1kg difference minimum (ie: 1, 2, 3) sand wouldn't make enough of a difference to obtain 5 different masses

Thanks thought!
 
13188920:McLS said:
thought about it but i need the masses to be of 1kg difference minimum (ie: 1, 2, 3) sand wouldn't make enough of a difference to obtain 5 different masses

Thanks thought!
Click to expand...

just so you know you could probably get 100kg+ out of an exercise ball full of water. now, sand has a much higher specific gravity than water, especially when its wet.
 
Here is a 15kg sand medicine ball thing. (1kg+2kg+3kg+4kg+5kg=15kg). I think that something like this is what would work well. I know this one is a bit pricey for a science project but I'm sure you could find one for cheaper. Even if it isn't removable sand made, you could probably cut a hole in it and put duct tape over it or something. Hope this helped

http://www.ironedge.com.au/store/15kg-dead-ball.html
 
Ok the way I see it your biggest problem is getting an even weight distribution, to avoid moments affecting your measurements.

5L capacity is kinda about what you want, gives an internal radius of 10.61cm according to wolfram alpha, round up to 11cm external radius.

I overthought that a little bit, you want a size 5 soccer ball.

Even weight distribution is a bit harder. You can fill the ball with water to make it 5kg, but when you start to take away water in place of air you get a bubble which floats around too much.

The obvious way round this is a two-component system where the density changes based on the composition, but to my knowledge there is no system where we have that much control over the density.

So we need another way.

Possibly... Get a size 6 soccer ball, cut it in half and tape it back together with a measured quantity of duct tape. Weigh the empty ball. Get a lot of really cheap ping pong balls. Using a drill, put small holes in some of them. Hold the holed balls underwater until bubbles stop coming out, and carefully reseal the ball using duct tape. Now you have heavy ping pong balls (filled with water), and light balls still filled with air. By altering the composition of heavy and light balls you place in the soccer ball you can control both the final mass of the soccer ball and the weight distribution. Make sure you use the same length of duct tape each time.

That weigh you should be able to get a ball that weighs between less than 1kg and more than 5kg, and everywhere in-between.

Correction: you can't actually get a size 6 soccer ball. A cheap basketball will do, and is probably built better for the task.
 
Just fill them evenly with different substances of differing density. You'll avoid the moment/distribution issues that way. Use sand, water, cotton candy, anything.
 
So, with all the Google in the world you are telling me you can't find a ball that you can put up to 5kg of water (that is 5l dumbass)?

Talk about stupid and unmotivated.
 
13188986:*DUMBCAN* said:
Ok the way I see it your biggest problem is getting an even weight distribution, to avoid moments affecting your measurements.

5L capacity is kinda about what you want, gives an internal radius of 10.61cm according to wolfram alpha, round up to 11cm external radius.

I overthought that a little bit, you want a size 5 soccer ball.

Even weight distribution is a bit harder. You can fill the ball with water to make it 5kg, but when you start to take away water in place of air you get a bubble which floats around too much.

The obvious way round this is a two-component system where the density changes based on the composition, but to my knowledge there is no system where we have that much control over the density.

So we need another way.

Possibly... Get a size 6 soccer ball, cut it in half and tape it back together with a measured quantity of duct tape. Weigh the empty ball. Get a lot of really cheap ping pong balls. Using a drill, put small holes in some of them. Hold the holed balls underwater until bubbles stop coming out, and carefully reseal the ball using duct tape. Now you have heavy ping pong balls (filled with water), and light balls still filled with air. By altering the composition of heavy and light balls you place in the soccer ball you can control both the final mass of the soccer ball and the weight distribution. Make sure you use the same length of duct tape each time.

That weigh you should be able to get a ball that weighs between less than 1kg and more than 5kg, and everywhere in-between.

Correction: you can't actually get a size 6 soccer ball. A cheap basketball will do, and is probably built better for the task.
Click to expand...

This is a cool idea, I'd be interested to try it. You're gonna be awesome at helping your kids with their science fair projects.
 
13189395:cobra_commander said:
So, with all the Google in the world you are telling me you can't find a ball that you can put up to 5kg of water (that is 5l dumbass)?

Talk about stupid and unmotivated.
Click to expand...

not even nasa could solve this
 
13189395:cobra_commander said:
So, with all the Google in the world you are telling me you can't find a ball that you can put up to 5kg of water (that is 5l dumbass)?

Talk about stupid and unmotivated.
Click to expand...

Water will slosh around and carry inertia unpredictably. Perhaps you should know what you're talking about before you talk shit.
 
13189575:Miomo said:
Water will slosh around and carry inertia unpredictably. Perhaps you should know what you're talking about before you talk shit.
Click to expand...

The water will slosh around, and carry inertia just as predictably as the result of this science project. If you can't predict what it is, you too are a complete fucking idiot.

Proceed to find the nearest wall made of concrete, brick, or similar material, and smash fuck your face with it.
 
can you shoot expandable spray foam in there? figure out how long you have to hold it down for each weight
 
13188986:*DUMBCAN* said:
Ok the way I see it your biggest problem is getting an even weight distribution, to avoid moments affecting your measurements.

5L capacity is kinda about what you want, gives an internal radius of 10.61cm according to wolfram alpha, round up to 11cm external radius.

I overthought that a little bit, you want a size 5 soccer ball.

Even weight distribution is a bit harder. You can fill the ball with water to make it 5kg, but when you start to take away water in place of air you get a bubble which floats around too much.

The obvious way round this is a two-component system where the density changes based on the composition, but to my knowledge there is no system where we have that much control over the density.

So we need another way.

Possibly... Get a size 6 soccer ball, cut it in half and tape it back together with a measured quantity of duct tape. Weigh the empty ball. Get a lot of really cheap ping pong balls. Using a drill, put small holes in some of them. Hold the holed balls underwater until bubbles stop coming out, and carefully reseal the ball using duct tape. Now you have heavy ping pong balls (filled with water), and light balls still filled with air. By altering the composition of heavy and light balls you place in the soccer ball you can control both the final mass of the soccer ball and the weight distribution. Make sure you use the same length of duct tape each time.

That weigh you should be able to get a ball that weighs between less than 1kg and more than 5kg, and everywhere in-between.

Correction: you can't actually get a size 6 soccer ball. A cheap basketball will do, and is probably built better for the task.
Click to expand...

Thank you soo much for taking the time dude!!! This is really helping!!! The ping pong balls are a great idea for better control, i love it! I think ill use a basketball and try things out, probably use the ping pong balls. Thanks man!!!!

13189395:cobra_commander said:
So, with all the Google in the world you are telling me you can't find a ball that you can put up to 5kg of water (that is 5l dumbass)?

Talk about stupid and unmotivated.
Click to expand...

Thank you sir for your formidably useful input.

13189744:Chubbs. said:
can you shoot expandable spray foam in there? figure out how long you have to hold it down for each weight
Click to expand...

Thats a great idea too, ill look into that, maybe a solidifying spray thing, and maybe ones with different densities, would be great.

STOKED ON THE HELP NS!!!! +k to all who helped!!!
 
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