Physics Challenge

Physics Challenge

You are given two spheres that are identical in size, weight, appearance, and touch but one sphere is hollow while the other is solid. (As an example, the solid sphere could be made out of a light wood and the hollow sphere made out of a denser wood, then both spheres carefully painted to look and feel the same.) Using only simple items that you might find at home (no fancy equipment, no drills, no X-ray machines), determine which sphere is hollow.

On 11/6/12 11:48 AM, Sam Wormley wrote:
Physics Challenge

You are given two spheres that are identical in size, weight,
appearance, and touch but one sphere is hollow while the other is
solid. (As an example, the solid sphere could be made out of a light
wood and the hollow sphere made out of a denser wood, then both
spheres carefully painted to look and feel the same.) Using only
simple items that you might find at home (no fancy equipment, no
drills, no X-ray machines), determine which sphere is hollow.



Oops, wrong newsgroup. Sorry about that!

Chris Schram wrote:
In article ,
Sam Wormley wrote:

On 11/6/12 11:48 AM, Sam Wormley wrote:
Physics Challenge

You are given two spheres that are identical in size, weight,
appearance, and touch but one sphere is hollow while the other is
solid. (As an example, the solid sphere could be made out of a light
wood and the hollow sphere made out of a denser wood, then both
spheres carefully painted to look and feel the same.) Using only
simple items that you might find at home (no fancy equipment, no
drills, no X-ray machines), determine which sphere is hollow.



Oops, wrong newsgroup. Sorry about that!

Wrong newsgroup? Yes. Provocative problem? Definitely.


Spin them?
The hollow one should spin for longer

On Nov 6, 8:50*pm, Chris Schram wrote:

Wrong newsgroup? Yes. Provocative problem? Definitely.
..
Really? Just tap each of them in turn with something hard and listen.
Or knock them together while each, in turn, is rested in the palm and
listen. They will not sound remotely alike. The hollow ball will sound
hollow.

In article
-septem
ber.org,
Mike Collins wrote:

Chris Schram wrote:
In article ,
Sam Wormley wrote:

On 11/6/12 11:48 AM, Sam Wormley wrote:
Physics Challenge

You are given two spheres that are identical in size, weight,
appearance, and touch but one sphere is hollow while the other is
solid. (As an example, the solid sphere could be made out of a light
wood and the hollow sphere made out of a denser wood, then both
spheres carefully painted to look and feel the same.) Using only
simple items that you might find at home (no fancy equipment, no
drills, no X-ray machines), determine which sphere is hollow.



Oops, wrong newsgroup. Sorry about that!

Wrong newsgroup? Yes. Provocative problem? Definitely.


Spin them?
The hollow one should spin for longer

Or role them down an incline plane. The hollow one should accelerate
slower.

On Tuesday, November 6, 2012 12:14:52 PM UTC-8, Chris.B wrote:
On Nov 6, 8:50*pm, Chris Schram wrote:



Wrong newsgroup? Yes. Provocative problem? Definitely.

.

Really? Just tap each of them in turn with something hard and listen.

Or knock them together while each, in turn, is rested in the palm and

listen. They will not sound remotely alike. The hollow ball will sound

hollow.

This might depend of your definition of *hollow*.

Imagine a 10-inch diameter bowling ball solid all the way through, and another made of a denser material with a 3-inch void in the exact center. That might still fit the *hollow"* definition. That void might be undetectable by just tapping. You would need to resolve the issue via alternate means.

\Paul A

"palsing" wrote in message ...
On Tuesday, November 6, 2012 12:14:52 PM UTC-8, Chris.B wrote:
On Nov 6, 8:50 pm, Chris Schram wrote:



Wrong newsgroup? Yes. Provocative problem? Definitely.

.

Really? Just tap each of them in turn with something hard and listen.

Or knock them together while each, in turn, is rested in the palm and

listen. They will not sound remotely alike. The hollow ball will sound

hollow.

This might depend of your definition of *hollow*.

Imagine a 10-inch diameter bowling ball solid all the way through, and another made of a denser material with a 3-inch void in the exact center. That might still fit the *hollow"* definition. That void might be undetectable by just tapping. You would need to resolve the issue via alternate means.

\Paul A

============================================
Good answer. Sometimes you DO think, palsing.
-- This message is brought to you from the keyboard of
Lord Androcles, Zeroth Earl of Medway

On Tuesday, November 6, 2012 5:03:44 PM UTC-8, Lord Androcles, Zeroth Earl of Medway wrote:
"palsing" wrote in message
...



On
Tuesday, November 6, 2012 12:14:52 PM UTC-8, Chris.B wrote:
On Nov 6,
8:50 pm, Chris Schram wrote:




Wrong newsgroup? Yes. Provocative problem?
Definitely.

.

Really? Just tap each of them in
turn with something hard and listen.

Or knock them together
while each, in turn, is rested in the palm and

listen. They
will not sound remotely alike. The hollow ball will sound


hollow.

This might depend of your definition of *hollow*.

Imagine
a 10-inch diameter bowling ball solid all the way through, and another made of a
denser material with a 3-inch void in the exact center. That might still fit the
*hollow"* definition. That void might be undetectable by just tapping. You would
need to resolve the issue via alternate means.

\Paul A


============================================

Good answer. Sometimes you DO think,
palsing.

--
This message is brought to you from the keyboard of
Lord Androcles, Zeroth
Earl of Medway

Why... thanks.

\Paul A

On 7 Nov., 00:51, palsing wrote:

This might depend of your definition of *hollow*.

Imagine a 10-inch diameter bowling ball solid all the way through, and another made of a denser material with a 3-inch void in the exact center. That might still fit the *hollow"* definition. That void might be undetectable by just tapping. You would need to resolve the issue via alternate means.

Okay then, let's try SPDT
(Standard Proxy Drop Test)

We drop Andrex and Squirrel repeatedly, head first, onto each ball, in
turn, from steadily increasing height.

One of them is certain to come up with a perfect answer in almost no
time at all.

And if they don't? We'll just call it basic research.
Then continue until the test apparatus becomes obsolete and is
replaced. (Funds permitting) :-)

On Nov 6, 12:11*pm, Mike Collins wrote:

Spin them?
The hollow one should spin for longer

No. The hollow one will spin for less time. There is more energy
stored in the solid spinning ball as it has a larger moment of
inertia. Energy drain is similar for both.

http://www.richardfisher.com