How many balls can fit into a jar

  • Context: MHB 
  • Thread starter Thread starter hatelove
  • Start date Start date
  • Tags Tags
    Balls Fit
Click For Summary

Discussion Overview

The discussion revolves around the problem of determining how many balls can fit into a jar, given specific dimensions for both the jar and the balls. Participants explore the implications of volume calculations, packing efficiency, and the effects of gaps between spheres when packed into a container.

Discussion Character

  • Exploratory, Technical explanation, Debate/contested, Mathematical reasoning

Main Points Raised

  • One participant calculates the volume of the jar and the balls, concluding that 648 balls can fit based on volume alone.
  • Another participant questions whether the calculation accounts for the spaces between the balls when packed into the jar.
  • A later reply mentions that the maximum packing fraction achievable is approximately 74% for regular packing and about 63% for random close packing.
  • One participant suggests an alternative approach to the calculation, emphasizing the use of fractions instead of decimals for clarity and ease of computation.
  • Another participant introduces the concept of a "density constant," proposing that the number of balls that can fit should be adjusted based on the ratio of the jar's dimensions to the balls' dimensions, suggesting a density constant of about 0.5 for the given dimensions.
  • They provide an example calculation for a different scenario involving smaller marbles and a larger jar, illustrating how the density constant varies with size.

Areas of Agreement / Disagreement

Participants express differing views on the significance of packing efficiency and the impact of gaps between the balls. There is no consensus on a definitive answer, as multiple approaches and considerations are presented.

Contextual Notes

The discussion highlights limitations related to assumptions about packing efficiency and the dependence on the specific dimensions of the jar and balls. The calculations presented do not resolve the complexities introduced by packing arrangements.

hatelove
Messages
101
Reaction score
1
The jar has a radius of 6" and a height of 24" and each ball has a radius of 1".

So I found the volume of the jar which is \pi6^{2}(24) = \approx 2,714.33605 and the volume of the balls which is \frac{4}{3}\pi1^{3} = \approx 4.1887902

And then I divided how many of the balls can go into the jar by dividing:

2714.33605 \div 4.1887902 = 648 balls

Does that number take into account the spaces between the balls when put into the jar? Like the small gaps when spheres are placed next to each other.
 
Physics news on Phys.org
daigo said:
The jar has a radius of 6" and a height of 24" and each ball has a radius of 1".

So I found the volume of the jar which is \pi6^{2}(24) = \approx 2,714.33605 and the volume of the balls which is \frac{4}{3}\pi1^{3} = \approx 4.1887902

And then I divided how many of the balls can go into the jar by dividing:

2714.33605 \div 4.1887902 = 648 balls

Does that number take into account the spaces between the balls when put into the jar? Like the small gaps when spheres are placed next to each other.

No, the maximum packing fraction that can be achieved with regular packing and no boundary effects is ~74%, and the random close packing packing fraction is ~63%.

See: >>here<< and >>here<<

CB
 
Hello, daigo!

The jar has a radius of 6" and a height of 24" and each ball has a radius of 1".
How many balls can fit into the jar?

So I found the volume of the jar which is: \pi6^{2}(24) = \approx 2,714.33605
and the volume of the balls which is: \frac{4}{3}\pi1^{3} = \approx 4.1887902

And then I divided how many of the balls can go into the jar by dividing:
. . ]2714.33605 \div 4.1887902 = 648\:balls

Does that number take into account the spaces between the balls when put into the jar? . . . . no
Like the small gaps when spheres are placed next to each other.
First of all, I'd do your math like this:

Volume of jar: \pi(6^2)(24) \:=\:864\pi

Volume of ball: \tfrac{4}{3}\pi(1^3)\:=\:\tfrac{4}{3}\pi

Therefore: .864\pi \div \tfrac{4}{3}\pi \:=\:648\text{ balls}

You see, I hate long (and incomplete) decimals.
. . I hate writing them down, I hate entering them on my calculator.
I would do anything (even Algebra) to avoid that.Second,you have melted the 648 balls into a puddle.
. . Then you poured the liquid into the jar.
 
daigo said:
The jar has a radius of 6" and a height of 24" and each ball has a radius of 1".

So I found the volume of the jar which is \pi6^{2}(24) = \approx 2,714.33605 and the volume of the balls which is \frac{4}{3}\pi1^{3} = \approx 4.1887902

And then I divided how many of the balls can go into the jar by dividing:

2714.33605 \div 4.1887902 = 648 balls

Does that number take into account the spaces between the balls when put into the jar? Like the small gaps when spheres are placed next to each other.

If the ratio of the dimensions of the jar compared to the dimensions of the diameter of the ball were large (it is not in this case), then the answer to the question of how many balls of 1 " radius could you put inside a jar of radius 6 " and a height of 24 " would be 648 times a "density constant" of about 0.5, or, 648 * 0.5 = 324. Let's call it 330 plus/minus 10. The larger the jar (and/or the smaller the marble), the higher the "density constant" would be. If you were figuring how many 5/8" diameter marbles (2 cc each) would go into a 1 gallon jar (3785 cc's), for example, the calculations would be:

3785/2*0.6 = 1324.75

or about 1330 plus/minus 10 marbles. The "density constant" here is 0.6. If you have a VERY LARGE container with VERY SMALL marbles, the density constant would be a maximum of 0.74.

https://www.physicsforums.com/threads/advanced-or-simple-balls-in-a-jar-probability.817893/
 
Last edited by a moderator:

Similar threads

  • · Replies 1 ·
Replies
1
Views
3K
  • · Replies 22 ·
Replies
22
Views
3K
  • · Replies 4 ·
Replies
4
Views
7K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 6 ·
Replies
6
Views
3K
Replies
2
Views
3K
  • · Replies 2 ·
Replies
2
Views
3K
  • · Replies 7 ·
Replies
7
Views
2K
Replies
2
Views
1K