TonyMcC

This is not something I have done. I usually just save any files I want to an external hard disc and then transfer them back to the new computer. However here is another link specifically about Windows 98 to XP transfer. http://www.ehow.com/how_2052293_copy-files-from-windows-98.html

Here is an official link - http://www.intel.com/content/www/us/en/tech-tips-and-tricks/how-to-transfer-files-to-a-new-compute.html For myself, most of what I want to keep is either in "my documents" or "my pictures". In that case saving these two files to a hard disc will make them available for transferring back to the new computer. However, my computer needs are simple and few!

I'm pleased to say there is evidence to the contrary - http://longevity-science.blogspot.com/2007/05/sex-and-longevity.html I rather suspect that a celibate life might just seem longer!

Assuming the crank pivot is on the centreline of the cylinder the height of the piston depends on the joining of two lines. A line from the crank pivot to the crank point and a line the length of the connecting rod. At top dead centre these will be a straight line. The slightest movement of the crank will destroy the straightness of the line and lower the height of the piston. That is why I think the time at top dead centre is an infinitely small instant of time leading me to the conclusion that the piston doesn't actually stop. (Not even for a picosecond ).

Time for a change of signature - I'm back on firm ground again! I'm glad to be back among the sane. Genuinely sincere apologies where needed and/or appropriate.

Rather like - there are 3 symptoms that indicate alzheimer's. The first is loss of memory and I forget the other two!

I would say that an instantaneous time of zero acceleration occurs at the mid point of the piston's travel and instantaneous speed of zero occurs at the top and bottom of the pistons travel. i.e a sine and cosine relationship. ( Neglecting the fact that even with a long connecting rod and small crank displacement there will be a little distortion of the sine and cosine waveforms)

The general consensus seems to be that although v=0 for an instant, at that time a<>0 and unless v and a are both zero at the same time the piston cannot be in a state fairly described as "stopped". (see #29 by Swansont)

Most people put a "signature" at the bottom of their posts. I change mine quite frequently in response to various thoughts. My first "signature" was a quote from the TV program "Bread" and was " The only good thing about getting old is that you don't have to give a bugger". Bearing in mind that I am quite old I thought it both apt and amusing. When I thought about it I decided it might be offensive to some of the members, so I changed it. Another "signature" that I have used is a quote by US senator Daniel Moynihan "You are entitled to your own opinions, but not your own facts". I chose this after a disagreement with a Staff Member as we clearly had different opinions concerning the word "opinion". My latest "signature" is "The road to Hell is paved with good intentions". There is someone who knows who I am and how to read my posts. This signature is a form of explanation and also an apology. Perhaps I should add "There is no fool like an old fool"! So - how much thought do you put into your signature and do you change it often?

Me also - I've enjoyed the discussion.

Wherever I look for a definition of "stop" it always implies "cease completely or for a time". I still think that as the piston passes through speed=0 in an infinitely small time it cannot be said to have stopped. I think v=0 is not sufficient by itself to define stop. I feel a proper definition of stop should be v=0 for a time. If it only paused for something like a picosecond I would say it stopped for a picosecond. But as it "stops" for an infinitely smaller time than that I question the statement that it can be said to have stopped at all. I do think we are really playing with words as I think we all know what happens. Its nearly bedtime now in UK so I wish you goodnight.

Now you have got me puzzled. If it is accelerating continuously then it is constantly changing its speed (unless it's something like a satellite). At some instant (of zero time) it will pass through a speed of zero. That isn't in dispute. But can you say it "stopped" as it went through the zero speed point of its cycle? Can we say that a body passing through a speed of zero in an infinitely small time can be said to have stopped?

As long as you accept that the piston never stops moving, and I accept that for an infinitely small period of time v=0 then there is no argument. There is a paradox in the statement that a body which is in continual motion can be said to have stopped at some point. I guess its a matter of semantics.

The piston doesn't move up and down the cylinder at uniform speed. Under the influence of the rotating crank it will be at its fastest in the mid point of its travel. On leaving the mid point, whether going up or down, it decelerates as it travels toward it highest (or lowest point) so that the change from going up to going down is a gradual process. However it is a continually changing process so if we are going to say the piston stopped it will be for an infinitely small time.

Not really, as it decelerates for the quarter cycle up to the top of its movement and then accelerates for the next quarter cycle as it leaves the top. There isn't a sudden snatched change of direction.

I'm not a mathematician, but I suppose it depends on what "S" and "c" might stand for and whether the formula has more than one application. Hopefully a mathematician will be able to shed some light.

Rather like Xittenn I often post for fun and sometimes a bit tongue in cheek although what I post I have considered first. Note that in this case my post was in the form of questions (not statements). I don't see the sine wave condition as an analogy as even if the the piston was in a stationary vehicle there is no reason why you can't plot its height with respect to time. I have no problem with the concept that an instant occupies zero time and therefore saying the piston remains stationary for zero time at each end of its travel. My experience has mostly been with electrical matters where often you have to calculate an instantaneous value of alternating voltage or current at a particular time. You calculate a definite value at a definite time. - not a range of values, however small, to accommodate a span of time, however small. So my question remains - if the piston "stops" for zero time can you say it stopped? Is there a flat spot, however small, on the top of a sine wave where there is no change in amplitude with respect to time? As I see it there is, but it is infinitely small.

The relevance to a sine wave is this -if a piston moves vertically in a cylinder then the height of the piston plotted against time is an approximate sine wave. If the connecting rod is very long compared with crank displacement from the centre line then the approximation is very accurate.

I think you might mean this - (1-a)C(pi)(r^2)=4(pi)(r^2)2εδ(T^4) If so, follow the link - http://arxiv.org/PS_cache/arxiv/pdf/0907/0907.5477v3.pdf

And you are happy to say there is an infinitely small flat area on the top of a sine wave?

The piston is stationary only for an instant. The question is "how long is an instant?" If the instant is infinitely small can the piston be said to have stopped? By a similar argument can you say that the top of a sine wave has a part that is flat and horizontal?

Actually Santa has perfected a system of perpetual motion and so his sleigh requires no power whatsoever.

Absolutely not. You are young and I am quite old and so it seemed a suitable reply when you consider the words of the puzzle. I really do hope you have a long and rewarding life - I haven't done so bad myself up to now.

Yep. Enjoy your long and rewarding life!