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where to post questions about introductory physics

where to post questions about introductory physics - Physics Forum

where to post questions about introductory physics - Physics Forum. Discuss and ask physics questions, kinematics and other physics problems.


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  #1  
Old 11-08-2004, 02:45 PM
ian bell
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Default where to post questions about introductory physics



Is there an appropriate newsgroup where questions about introductory physics
can be posted? I am slowly working my way through a high school physics
text book and would like to be able to post occasional questions. Would
someone be so good as to let me know if there is a newsgroup where I can
post my questions?

Ian


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  #2  
Old 11-08-2004, 08:54 PM
tadchem
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Default where to post questions about introductory physics


"ian bell" <[Only registered users see links. ]> wrote in message
news:cELjd.49714$[Only registered users see links. ]...
physics

If you are willing to try to separate the good from the bad, you can get all
kinds of answers here on alt.sci.physics. You can also try sci.physics.

Your news browser should be able to give you a list of other NGs with
".physics" in the name.

I have been hanging here for ? years doing exactly what you need, along with
several others, so give us a try.


Tom Davidson
Richmond, VA


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  #3  
Old 11-08-2004, 08:55 PM
tadchem
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Default where to post questions about introductory physics


"ian bell" <[Only registered users see links. ]> wrote in message
news:cELjd.49714$[Only registered users see links. ]...
physics

If you are willing to try to separate the good from the bad, you can get all
kinds of answers here on alt.sci.physics. You can also try sci.physics.

Your news browser should be able to give you a list of other NGs with
".physics" in the name.

I have been hanging here for ? years doing exactly what you need, along with
several others, so give us a try. Keep in mind that we *won't* do your
homework for you, but we will try to help you understand it, if you are
willing to learn.


Tom Davidson
Richmond, VA


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  #4  
Old 11-08-2004, 08:55 PM
tadchem
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Default where to post questions about introductory physics


"ian bell" <[Only registered users see links. ]> wrote in message
news:cELjd.49714$[Only registered users see links. ]...
physics

If you are willing to try to separate the good from the bad, you can get all
kinds of answers here on alt.sci.physics. You can also try sci.physics.

Your news browser should be able to give you a list of other NGs with
".physics" in the name.

I have been hanging here for ? years doing exactly what you need, along with
several others, so give us a try. Keep in mind that we *won't* do your
homework for you, but we will try to help you understand it, if you are
willing to learn.


Tom Davidson
Richmond, VA


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  #5  
Old 11-09-2004, 04:06 AM
tadchem
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Default where to post questions about introductory physics


"Ian" <[Only registered users see links. ]> wrote in message
news:sOXjd.27639$[Only registered users see links. ]. ..

<snip>

and

<snip>

The hint is that you have been studying "work and energy", specifically
non-conservative forces.

Since energy is one of those quantities that are normally considered to be
conserved, your examination should focus on the energy.

Ask yourself first "How much *energy* would it take to lift a 3.00 kg mass
100 m working against gravity?"

Second, ask "If 800 J is lost to air resistance, how much energy is left to
do the work of lifting the rocket?"

Finally, ask "How high could the *remaining* energy lift the rocket?"

(This pedagogic device has been brought to you by Socrates, in the hope that
you will also learn that much of scientific investigation consists in
learning how to ask questions that are easy to answer, based on what you
already know, that lead you to new knowledge in small increments.)


Tom Davidson
Richmond, VA


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  #6  
Old 11-09-2004, 04:34 AM
Ian
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Default where to post questions about introductory physics

Hello Tom,

Thanks for the quick response and I am delighted to learn you are willing to
try helping out.

High school physics was a source of great frustation to me - over 20 years
ago. I am "slowly' working through a physics text book as a personal
interest. There is no homework per se but I am dilgently plodding through
the questions provided at the end of each chapter. I've always found the
subject matter to be a challenge to understand so be forwarned I am slow to
grasp this material.

For references purposes, the text book I have is titled 'Physics - 3rd
edition', by John, D. Cutnell and Kenneth W. Johnson, 1995.

Now, for my question. I've just finished the chapter on work and energy and
the answer to question #57 at the end of the chapter eludes me. It deals
with the concept of nonconservative forces and the work-energy theorem:
"A 3.00-kg model rocket is launched vertically straight up with
sufficient initial speed to reach a maximum height of 100m,
even though air resistance (a nonconservative force) performs -800J of
work on the rocket. How high would the rocket
have gone without air resistance"? The answer provided is 127m.

I spent a considerable amount of time on this question but have to admit
this one has me beat. Would you so good as to provide either provide me
with the solution, or failing that, a 'strong' hint?

Many thanks,

Ian




"tadchem" <[Only registered users see links. ]> wrote in message
news:[Only registered users see links. ]...


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  #7  
Old 11-09-2004, 07:03 PM
Martin Hogbin
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Default where to post questions about introductory physics


"Ian" <[Only registered users see links. ]> wrote in message news:sOXjd.27639$[Only registered users see links. ]. ..

You are supposed to assume that the rocket motor provides the
same amount of energy in both cases which is not always realistic -
no matter). You know the final potential energy of the rocket and
the energy lost through air resistance.

Martin Hogbin


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  #8  
Old 11-09-2004, 08:37 PM
Ian
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Default bingo

Hi Dave,

Finally got it, thanks entirely to your re-direction.
h2 = (mgh1 + WR) / (mg) = [(3kg)(9.8m/s/s)(100m) + 800J] /
(3.0kg)(9.8m/s/s) = 127.21m

You would have gotten a chuckle out of the convoluted approach I had taken
on my own accord.

I appreciate your time and effort.

Thanks again.

Ian


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  #9  
Old 11-09-2004, 08:45 PM
Ian
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Default where to post questions about introductory physics

Hello Martin,

I was able to work this problem through early this morning following the
help offered by Tom. I spent the past few hours celebrating by raking up
the leaves in the back yard.

It was kind of you to take the time to respond.

Thanks

Ian



"Martin Hogbin" <[Only registered users see links. ]> wrote in message
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  #10  
Old 11-10-2004, 12:05 AM
N:dlzc D:aol T:com \(dlzc\)
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Default bingo

"Ian" <[Only registered users see links. ]> wrote in message
news:HU9kd.69518$[Only registered users see links. ].. .

I think he was directing this response to Tom Davidson...



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