This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is simultaneously
attached to the surface of the rotating cylinder. (Assume the rod is
made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached to
the rotating cylinder 1.73 seconds before the other end. That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern. (The moving frame measures the attached rod to be a straight
line at any instant of time as measured in the moving frame).

We let the attached rod and cylinder rotate for however long is
necessary to achieve a steady-state condition for the shape of the
rod. We then change the chemical composition of the attached rod so
that it is no longer malleable. It becomes rigid and fixed in that
shape and requires an extremely large force to change its shape.

Now, after this occurs, at time t1 as measured in the moving frame,
each attachment point which connects the rod to the rotating cylinder
is eliminated so that the rod is no longer attached to the cylinder.
Let's say this occurs at the instant (as measured in the moving frame)
when all the y coordinates of the rod are zero so that the rod begins
moving only in the X-Y plane. Observers in the moving frame measure a
straight rod traveling in the X-Y plane, and this rod has zero
rotation rate.

Using Einstein's notions, I don't see how to explain things from the
point of view of observers in the stationary frame. In this frame,
the rod is a rigid spiral wrapped 17 times around a cylinder. When
the contact with the cylinder is eliminated, there must be some force
which straightens the spiral shaped rod as the rod is unwrapped from
the cylinder, and this must occur in 1.73 seconds. When the rod was
initially wrapped around the cylinder, this force came from the
cylinder and the force required was minimal since the rod was
extremely malleable at that time (the given information). However, in
unwrapping the rod from the cylinder, the force comes from the
chemical bonds throughout the rod. The force is applied through
chemical bonds, and the contact points are eliminated far faster than
any chemical bond can react. So how can you make the views in the two
frames agree?
David Seppala

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is simultaneously
attached to the surface of the rotating cylinder. (Assume the rod is
made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached to
the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern.

Nope. From the stationary frame, the rod was rotating along with the line
drawn straight along the surface of the cylinder drawn by a laser level
device before the rod was ever joined to the cylinder.

The stationary observer is intellegent enough to realize that light moves
in a straight line[in the rotating FoR] and that the optical delusion of a
17 times wrap is exactly that.

(The moving frame measures the attached rod to be a straight
line at any instant of time as measured in the moving frame).

We let the attached rod and cylinder rotate for however long is
necessary to achieve a steady-state condition for the shape of the
rod. We then change the chemical composition of the attached rod so
that it is no longer malleable. It becomes rigid and fixed in that
shape and requires an extremely large force to change its shape.

Now, after this occurs, at time t1 as measured in the moving frame,
each attachment point which connects the rod to the rotating cylinder
is eliminated so that the rod is no longer attached to the cylinder.
Let's say this occurs at the instant (as measured in the moving frame)
when all the y coordinates of the rod are zero so that the rod begins
moving only in the X-Y plane. Observers in the moving frame measure a
straight rod traveling in the X-Y plane, and this rod has zero
rotation rate.

Using Einstein's notions, I don't see how to explain things from the
point of view of observers in the stationary frame. In this frame,
the rod is a rigid spiral wrapped 17 times around a cylinder. When
the contact with the cylinder is eliminated, there must be some force
which straightens the spiral shaped rod as the rod is unwrapped from
the cylinder, and this must occur in 1.73 seconds. When the rod was
initially wrapped around the cylinder, this force came from the
cylinder and the force required was minimal since the rod was
extremely malleable at that time (the given information). However, in
unwrapping the rod from the cylinder, the force comes from the
chemical bonds throughout the rod. The force is applied through
chemical bonds, and the contact points are eliminated far faster than
any chemical bond can react. So how can you make the views in the two
frames agree?
David Seppala

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

When I look at myself in a funhouse mirror, I know that I really do NOT get
long and thin or short and fat. When I look at something in another FoR, I
know that things look different from that FoR.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

wrote in message ...
This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

Another everyday experience problem with 300000 km long
rigid rods, I presume?
http://users.pandora.be/vdmoortel/di.../Everyday.html

[snip unread]

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

Was I right?

Dirk Vdm

I think that you ought to think of something hapening in the stationary
frame, thisd is after all the freame that contains both the cylinder
and the rod and see what the viewpoint is in the moving frame.

If indeed the view from the moving frame is as you describe then the
rod does indeed wrap itself round the cylinder 1.7 times. That is
however a posulate that might in fact not be the case in fact. Another
thing we have to remember is that the rod is only 10m across but is
300000 km long. This means that the rod can wrap round without too much
difficulty.

OK you may say this is really evading the question - Not really because
according to relativity the speed of sound = c. (Usually in practical
materials c). Hence in 300000km even the theoretically rigid rods
will bend

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is simultaneously
attached to the surface of the rotating cylinder. (Assume the rod is
made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached to
the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern.

Nope. From the stationary frame, the rod was rotating along with the line
drawn straight along the surface of the cylinder drawn by a laser level
device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.

The stationary observer is intellegent enough to realize that light moves
in a straight line[in the rotating FoR] and that the optical delusion of a
17 times wrap is exactly that.

(The moving frame measures the attached rod to be a straight
line at any instant of time as measured in the moving frame).

We let the attached rod and cylinder rotate for however long is
necessary to achieve a steady-state condition for the shape of the
rod. We then change the chemical composition of the attached rod so
that it is no longer malleable. It becomes rigid and fixed in that
shape and requires an extremely large force to change its shape.

Now, after this occurs, at time t1 as measured in the moving frame,
each attachment point which connects the rod to the rotating cylinder
is eliminated so that the rod is no longer attached to the cylinder.
Let's say this occurs at the instant (as measured in the moving frame)
when all the y coordinates of the rod are zero so that the rod begins
moving only in the X-Y plane. Observers in the moving frame measure a
straight rod traveling in the X-Y plane, and this rod has zero
rotation rate.

Using Einstein's notions, I don't see how to explain things from the
point of view of observers in the stationary frame. In this frame,
the rod is a rigid spiral wrapped 17 times around a cylinder. When
the contact with the cylinder is eliminated, there must be some force
which straightens the spiral shaped rod as the rod is unwrapped from
the cylinder, and this must occur in 1.73 seconds. When the rod was
initially wrapped around the cylinder, this force came from the
cylinder and the force required was minimal since the rod was
extremely malleable at that time (the given information). However, in
unwrapping the rod from the cylinder, the force comes from the
chemical bonds throughout the rod. The force is applied through
chemical bonds, and the contact points are eliminated far faster than
any chemical bond can react. So how can you make the views in the two
frames agree?
David Seppala

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

When I look at myself in a funhouse mirror, I know that I really do NOT get
long and thin or short and fat. When I look at something in another FoR, I
know that things look different from that FoR.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

wrote in
:

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is simultaneously
attached to the surface of the rotating cylinder. (Assume the rod is
made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached to
the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern.

Nope. From the stationary frame, the rod was rotating along with the
line drawn straight along the surface of the cylinder drawn by a laser
level device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.


You have a slight problem.
you said:
In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

That puts one end of the rod and some [poorly specified] point on the
rotating cylinder at the same point.

If I assume the point is on the circumference of the cylinder rather than
the center of the cylender [that would make for all kinds of problems] then
you have infinite acceleration of the rod at the moment of attachment.

Only if the rod is already in motion, can it be attached to the cylinder.


The stationary observer is intellegent enough to realize that light
moves in a straight line[in the rotating FoR] and that the optical
delusion of a 17 times wrap is exactly that.

.....

When I look at myself in a funhouse mirror, I know that I really do NOT
get long and thin or short and fat. When I look at something in another
FoR, I know that things look different from that FoR.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

wrote in message
...

[snip]
We let the attached rod and cylinder rotate for however long is
necessary to achieve a steady-state condition for the shape of the
rod. We then change the chemical composition of the attached rod so
that it is no longer malleable. It becomes rigid and fixed in that
shape and requires an extremely large force to change its shape.

Now, after this occurs, at time t1 as measured in the moving frame,
each attachment point which connects the rod to the rotating cylinder
is eliminated so that the rod is no longer attached to the cylinder.
Let's say this occurs at the instant (as measured in the moving frame)
when all the y coordinates of the rod are zero so that the rod begins
moving only in the X-Y plane. Observers in the moving frame measure a
straight rod traveling in the X-Y plane, and this rod has zero
rotation rate.


Did you mean to say 'when all the *z* coordinates of the rod are zero...' ?

Also, why would the z-component of motion suddenly cease when the
attachments are eliminated at the instant the rod is in the X-Y plane?

Max

On Sat, 20 Aug 2005 22:55:42 +0000 (UTC), bz
wrote:

wrote in
:

On Fri, 19 Aug 2005 15:07:03 +0000 (UTC), bz
wrote:

wrote in news:4305d0b7.540887@news-
server.austin.rr.com:

This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

I have two frames which I will call the stationary frame and the
moving frame. Their relative velocity is 0.866 c. In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

As measured in the moving frame, let the length of the rod and the
length of the rotating cylinder be 1 light-second. At time t0 as
measured in the moving frame, each point of the rod is simultaneously
attached to the surface of the rotating cylinder. (Assume the rod is
made of a material that is very malleable).

As viewed in the stationary frame, one end of the rod was attached to
the rotating cylinder 1.73 seconds before the other end.

Ok.

That means
that the rod wrapped around the cylinder about 17 times in a spiral
pattern.

Nope. From the stationary frame, the rod was rotating along with the
line drawn straight along the surface of the cylinder drawn by a laser
level device before the rod was ever joined to the cylinder.
No. The rod develops a rotation because it is attached to the
rotating cylinder. Prior to being attached, the rod is not rotating
and has zero velocity wrt to the longitudinal axis of the cylinder.


You have a slight problem.
you said:
In the stationary
frame, parallel to the x-axis there is a rod and a rotating cylinder.
The end points of the rod and the rotating cylinder are at the same x
coordinates. The diameter of the cylinder is 10 meters and the
cylinder is rotating at 10 revolutions per second.

That puts one end of the rod and some [poorly specified] point on the
rotating cylinder at the same point.

If I assume the point is on the circumference of the cylinder rather than
the center of the cylender [that would make for all kinds of problems] then
you have infinite acceleration of the rod at the moment of attachment.

Only if the rod is already in motion, can it be attached to the cylinder.
No. The circumference of the rotating cylinder is about 31 meters.
At 10 revolutions per second, the surface of the cylinder is moving at
about 310 meters / second. Let's say the cylinder contains an
extremely powerful electromagnet, and the rod is steel. When the
magnet is turned on, if the force is strong enough, the magnet will
keep the rod attached to the rotating cylinder. There are thousands
of ways to do this attachment. Surely, you agree that if the rotation
speed is very low, say 0.001 revolutions per second, there would be no
problem attaching the rod to the cylinder - you can do this experiment
with short rod segments. I only picked 10 revolutions per second so
that its easier to envision the rod spiraled completely around the
cylinder as opposed to spiraled over a very small angle.
David


The stationary observer is intellegent enough to realize that light
moves in a straight line[in the rotating FoR] and that the optical
delusion of a 17 times wrap is exactly that.

....

When I look at myself in a funhouse mirror, I know that I really do NOT
get long and thin or short and fat. When I look at something in another
FoR, I know that things look different from that FoR.




--
bz

please pardon my infinite ignorance, the set-of-things-I-do-not-know is an
infinite set.

remove ch100-5 to avoid spam trap

On Sun, 21 Aug 2005 19:29:14 GMT, "Max" wrote:


wrote in message
...

[snip]
We let the attached rod and cylinder rotate for however long is
necessary to achieve a steady-state condition for the shape of the
rod. We then change the chemical composition of the attached rod so
that it is no longer malleable. It becomes rigid and fixed in that
shape and requires an extremely large force to change its shape.

Now, after this occurs, at time t1 as measured in the moving frame,
each attachment point which connects the rod to the rotating cylinder
is eliminated so that the rod is no longer attached to the cylinder.
Let's say this occurs at the instant (as measured in the moving frame)
when all the y coordinates of the rod are zero so that the rod begins
moving only in the X-Y plane. Observers in the moving frame measure a
straight rod traveling in the X-Y plane, and this rod has zero
rotation rate.


Did you mean to say 'when all the *z* coordinates of the rod are zero...' ?
I should have been clearer. I envisioned the surface of the cylinder
to be touching the x-axis. When all points of the attached rod as
viewed in the moving frame are also coincident with the x-axis, the
attachment points are all eliminated (at time t1 as viewed in the
moving frame).

Also, why would the z-component of motion suddenly cease when the
attachments are eliminated at the instant the rod is in the X-Y plane?
This is the view in the moving frame. In the moving frame the rod is
measured to be a straight line. When the rod as viewed in the moving
frame is at the top of the cylinder circumference, and all attachment
points are eliminated at the same time as viewed in this frame, the
straight rod should remain a straight rod since no force acted on it
to bend it. But this view conflicts with what observers in the
stationary frame see. That is the reason for this post
David

Max

On Fri, 19 Aug 2005 16:27:39 GMT, "Dirk Van de moortel"
wrote:


wrote in message ...
This problem is a combination of several problems I've posted in this
group. When I combine the problems, the answers given to me in
previous posts don't work. Here's the problem.

Another everyday experience problem with 300000 km long
rigid rods, I presume?
http://users.pandora.be/vdmoortel/di.../Everyday.html

Dirk, the link you posted has pandora.be in it, from which I infer
refers to a country different than the United States of America. So
I'm guessing English is not your native language. If you carefully
read my sentence that you refer to in the above link, you will see
that I stated that the 300000 km length IS NOT part of my everyday
experience. If you carefully read what I posted, you will see that
the sentence begins with the word "Other". "Other" when used in this
context means "with the exception of". The meaning of the sentence I
posted is that the 300000 km length IS NOT in my everyday experience,
but the 3 meter per second velocity is in my everyday experience, and
the accleration from 0 to 3 meters per second in 0.1 seconds is in my
everyday experience.
There are some good dictionaries available online
http://www.m-w. com
for example. If you look up the definition of "other" you will see
that first definition is "being the one not included" So in
everyday English as used in the USA, the sentence I posted means that
the 300000 km rod is the parameter that is NOT part of my everyday
experience.
Hope that helps you're understanding of this common English usage.
David

[snip unread]

Please note: If you don't know the physics answer, please feel free
to put up a post that includes personal attacks of my intelligence and
education. That's the approach used by the vast majority of the
people on the planet when they can't logically explain something, so
why should you be different? Besides, your peers may join in giving
each of you mutual support.

Was I right?

Dirk Vdm