How many tennis balls can fit in a room?

[infinite]

The diameter of a tennis ball is 2.63 in. The size of a particular room is 43 ft X 10.5 ft X 30 ft. How many tennis balls can fit in this room?

[Greg H.]

It depends on how they end up stacked. If you assume the least optimal stacking method (treating each ball like a cube with a side equal to the diameter of the ball), the minimum number is 1,286,635 (give or take).

 

Edit to add

 

You'd also have to assume that the tennis balls on the lowest tiers of the stack do not deflect from the weight of the ones on top of them.

Edited August 31, 2012 by Greg H.

[imatfaal]

1. This question is a great example of why we should all use metric measurement.

 

2.

Room volume 2.3 x10^6 cubic inches

Ball volume 9.5 cubic inches

Maxium possible packing density pi/sqrt(18)

Max Number of possible balls 1.8x10^6

 

There is a fairly chunky error and is an over approximation as there will be gaps at walls and corners. This is based on the greengrocer stack (each layer is hexagonal array like honeycomb and each ball of next layer fits in dip between three) which Gauss proved in the 19th century was the most efficient regular packing of spheres. We have recently seen almost proofs in which computers have (almost) exhaustively searched irregular packing and the greengrocer stack is still the most efficient

[Phi for All]

Sounds like a homework question.

[imatfaal]

Sounds like a homework question.

 

Zut! Should have noticed that - oh well Greg and I have answered it now.

[Greg H.]

1. This question is a great example of why we should all use metric measurement.

 

2.

Room volume 2.3 x10^6 cubic inches

Ball volume 9.5 cubic inches

Maxium possible packing density pi/sqrt(18)

Max Number of possible balls 1.8x10^6

 

There is a fairly chunky error and is an over approximation as there will be gaps at walls and corners. This is based on the greengrocer stack (each layer is hexagonal array like honeycomb and each ball of next layer fits in dip between three) which Gauss proved in the 19th century was the most efficient regular packing of spheres. We have recently seen almost proofs in which computers have (almost) exhaustively searched irregular packing and the greengrocer stack is still the most efficient

 

So that's why they stack fruit that way. I never knew that.

[imatfaal]

You will note that Mathworld states that the Kepler Conjecture (that Hexagonal Close Packing is the most efficient of any form) has been proved, whilst Wikipedia is only almost certain. It's such a simple problem - and greengrocer's automatically do it - but it taxed the minds of Gauss and Kepler to name but two of those who have worked on it (but what a pair of minds!)

 

 

http://www.maa.org/devlin/devlin_9_98.html

http://en.wikipedia.org/wiki/Sphere_packing

http://mathworld.wolfram.com/SpherePacking.html

[Fuzzwood]

So that's why they stack fruit that way. I never knew that.

 

Body centered cubic. You even find that type of stacking between atoms.

[John Cuthber]

Actually it's perfectly possible to get ten times that number of tennis balls into the room.

But not all at the same time

[Phi for All]

Actually it's perfectly possible to get ten times that number of tennis balls into the room.

But not all at the same time

I could do it. If they're still considered tennis balls after being shredded.

[Greg H.]

I could do it. If they're still considered tennis balls after being shredded.

 

Do shredded tennis balls still have a diameter?

Edited August 31, 2012 by Greg H.

[Phi for All]

Do shredded tennis balls still have a diameter?

Depends on how finely shredded they are. At some measurable level I'm sure they would.

[dimreepr]

Depends on how finely shredded they are. At some measurable level I'm sure they would.

 

Is a ball still a ball when deflated?

 

 

[Phi for All]

Is a ball still a ball when deflated?

If you saw one under your car tire, you'd still say, "What the heck is... oh, it's a tennis ball."