Re: perpetual motion ahoy!

[Doug Craigen <dcc@cyberspc.mb.ca>]

On Thu, 22 May 1997, William Beaty wrote:

> Anyone interested in "PM" machines?  A hobbyist in Australia has managed
> to make a steel ball roll up a magnet-lined slope, then fall over the edge
> and roll away! 
>
> Does anyone have opinions on how this could occur without violating
> conservation of energy?

I personally take an interest in perpetual motion machines.  Assuming this
machine does what is claimed it would be interesting to see the design.
It is not hard to imagine designs that would genuinely accomplish the
claims without violating energy conservation.  For example, consider the
following sketch:
       N

    /|
   / |
  /  |
O/t  |R

the steel ball O (use mumetal for a better demonstration) rolls up a
gentle slope at small angle t, pulled by the north end of a long magnet.
Before it actually reaches the magnet pole, the slope becomes a dropoff.
The magnetic force which was sufficient to overcome a small vertical
component of weight due to gravity is not strong enough to support the
whole weight of the ball, and it drops to its final resting spot R.  All
of this is easily accomplished and there has been a net expense of
mechanical energy which could be converted to useful purposes...

To the non-technical, it may be believed that this has demonstrated a
violation of energy conservation, but that is because they don't realize
that all energy has been kept track of very handily and they will have to
use up all the excess they had gained in order to get the ball back to its
starting position at the bottom of the ramp.

If the magnetic design of the Australian hobbyist is more complex than
this it is just bells and whistles rather than real substance.  The thing
that he will have to demonstrate to show that his device violates energy
conservation is not that it rolls away, but that if appropriate tracks or
grooves are put in place to guide it, that it can go rolling back to the
starting position and arrive there with a speed > 0.

|++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++|
| Doug Craigen                                                 |
|                                                              |
| If you think Physics is no laughing matter, think again .... |
|    http://cyberspc.mb.ca/~dcc/phys/humor.html                |
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