Subject:
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Falling thru earth revisited
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Newsgroups:
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lugnet.off-topic.geek
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Date:
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Wed, 8 Jun 2005 18:23:28 GMT
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Viewed:
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2594 times
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'cause I've been ruminating about it....
So let's take this from the base model--
Base model ignores the following--
Rotation
AIr Resistance
you have the earth and a hole from where you are, going straight thru the center
and right out to the other side of the planet.
Person A drops something in the hole--if I understand, the object will
accellerate towards the center of the planet, and decellerate after reaching the
center of the planet, and should have a speed of 0 at the entrance to the hole
on the other side of the planet (before it falls back down into the hole).
Person A shoots a bullet from a gun right down the center of the hole--again, if
I understand, the bullet will accellerate towards the center of the planet,
decellerate after reaching the center of the planet, and should have the same
speed as it had when it was fired when it reaches the other side of the planet.
Person A has a rocket launcher and activates a rocket right down the center of
the hole. The rocket accellerates due to it's own propulsion as well as having
the added factor of gravity pulling down on it. The rocket will still continue
to propel itself, even when working against gravity after it reaches the center
of the planet, and the rocket will emerge at the other side of the hole.
How fast will the rocket be going?
My idea is that basically the accelleration of an object going towards the
center due to gravity and the decelleration of an object from the center to the
other side basically cancels out, so we would just have to measure the
distance/time from the entry point to the exit and figure in the thrust of the
rocket across that distance and we'd have a pretty good idea of how fast it'l
lbe going.
Which is a roundabout way of getting back to 'Lost in Space' and the idea that
the ship didn't have enough momentum to escape the gravity of the planet when it
went straight up, but did when it went through the planet.
I'm thinking now that it would work--
A rocket propelled straight up has little distance to build up momentum due to
thrust.
A rocket propelled straight through the planet has the diameter of the planet to
build up thrust, and the accelleration/decelleration due to gravity badically
cancels out.
But I could be wrong.
Dave K
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Message has 2 Replies:
 | | Re: Falling thru earth revisited
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| (...) One other thing to think about is the amount of time something's been exposed to something that increases its speed. For example: Uncle Ben and Aunt Jemima have a race from point A to point B, and back to point A. Aunt Jemima stays at a (...) (19 years ago, 8-Jun-05, to lugnet.off-topic.geek)
| | | Re: Falling thru earth revisited
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| (...) Sounds right to me. Acceleration adds linearly, so when you integrate to get the velocity, you have the integral of the thrust plus the integral of the gravitational acceleration. Assuming that the change in mass of the rocket due to depleted (...) (19 years ago, 8-Jun-05, to lugnet.off-topic.geek)
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