| Topic: |
Science > Physics |
| User: |
"Ishrogh" |
| Date: |
13 Nov 2003 10:31:05 AM |
| Object: |
Superball problem |
My colleagues and I were standing in the 10-storey atrium where we
work. It led to this question about force and gravity: A person
standing on the ground throws a rubber ball against the ground (we
called them super-balls as kids) and it bounces 25 feet into the air.
If that person takes the same rubber ball and throws it with the same
amount of force from three storeys high (30 feet) what's the maximum
height that rubber ball will bounce assuming it bounces straight up?
Why? If that person threw the ball from 10 storeys, would it bounce
back up 10 storeys? From what height wouldn't it return to the point
from which the person threw it? Thanks, Isobar
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| User: "Frank Reichenbacher" |
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| Title: Re: Superball problem |
13 Nov 2003 02:17:00 PM |
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"Ishrogh" <ishrogh@yahoo.com> wrote in message
news:447700ef.0311130831.2d59b7c6@posting.google.com...
My colleagues and I were standing in the 10-storey atrium where we
work. It led to this question about force and gravity: A person
standing on the ground throws a rubber ball against the ground (we
called them super-balls as kids) and it bounces 25 feet into the air.
If that person takes the same rubber ball and throws it with the same
amount of force from three storeys high (30 feet) what's the maximum
height that rubber ball will bounce assuming it bounces straight up?
Why? If that person threw the ball from 10 storeys, would it bounce
back up 10 storeys? From what height wouldn't it return to the point
from which the person threw it? Thanks, Isobar
When I was a kid I threw a superball off the downstream side of Hoover Dam.
Unfortunately it was so small I couldn't see where it hit. Presumably it
blew up and the pieces bounced quite a long ways, probably all the way to
the Colorado River.
You understand, of course, that this was a very long time ago, before
security was any kind of issue.
Frank
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| User: "Uncle Al" |
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| Title: Re: Superball problem |
13 Nov 2003 11:15:03 AM |
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Ishrogh wrote:
My colleagues and I were standing in the 10-storey atrium where we
work. It led to this question about force and gravity: A person
standing on the ground throws a rubber ball against the ground (we
called them super-balls as kids) and it bounces 25 feet into the air.
If that person takes the same rubber ball and throws it with the same
amount of force from three storeys high (30 feet) what's the maximum
height that rubber ball will bounce assuming it bounces straight up?
Why? If that person threw the ball from 10 storeys, would it bounce
back up 10 storeys? From what height wouldn't it return to the point
from which the person threw it? Thanks, Isobar
From whatever height under whatever circumstances, you get the initial
imparted kinetic energy and momentum plus mgh less air resistance. If
the ball hits beyond its elastic recovery limits it explodes. After
it hits normal to the rigid surface, less small internal frictional
loses, it bounces up and returns the mgh less air resistance, then
comes down and repeats.
Dropping a serial stack of graded size (mass) balls must conserve
momentum and energy. The old "Scientific American" had an excellent
Amateur Scientist column on it. Brute force is cute, but leverage
will more easily get you the big numbers.
http://mrsec.wisc.edu/edetc/amorphous/
then
http://mrsec.wisc.edu/edetc/cineplex/amorphous2.html
--
Uncle Al
http://www.mazepath.com/uncleal/
(Toxic URL! Unsafe for children and most mammals)
"Quis custodiet ipsos custodes?" The Net!
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| User: "Mark Folsom" |
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| Title: Re: Superball problem |
08 Dec 2003 01:54:17 AM |
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"Uncle Al" <UncleAl0@hate.spam.net> wrote in message
news:3FB3BC17.154DA93@hate.spam.net...
Ishrogh wrote:
My colleagues and I were standing in the 10-storey atrium where we
work. It led to this question about force and gravity: A person
standing on the ground throws a rubber ball against the ground (we
called them super-balls as kids) and it bounces 25 feet into the air.
If that person takes the same rubber ball and throws it with the same
amount of force from three storeys high (30 feet) what's the maximum
height that rubber ball will bounce assuming it bounces straight up?
Why? If that person threw the ball from 10 storeys, would it bounce
back up 10 storeys? From what height wouldn't it return to the point
from which the person threw it? Thanks, Isobar
From whatever height under whatever circumstances, you get the initial
imparted kinetic energy and momentum plus mgh less air resistance. If
the ball hits beyond its elastic recovery limits it explodes. After
it hits normal to the rigid surface, less small internal frictional
loses, it bounces up and returns the mgh less air resistance, then
comes down and repeats.
There's some vibration left behind in the struck body.
Mark Folsom
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