[sci.electronics] PUZZLE

yphotons@athena.mit.edu (Sun Warrior) (03/18/89)

Have any ideas??????

A recent MIT physics (freshman) extra-credit problem: Given 2 small
rectangular magnets, 2 paper clips, 2 thumb tacks, approx. 5 feet of
wire, a small block of wood (4"X2"X.5") build a DC motor running of 1
1.5V that can at least reach 2600 rpm. The use of glue, tape, etc in
the final product will disqualify you. Only the above mentioned items
can be in the final product. The use of a drill, saw, etc.  in
building the motor is ok.

dhesi@bsu-cs.UUCP (Rahul Dhesi) (03/20/89)

In article <9916@bloom-beacon.MIT.EDU> yphotons@athena.mit.edu writes:
>Have any ideas??????
[about making a DC electric motor out of magnets, paper clips,
thumbtacks, wire, and wood]

Check the early issues of Popular Science (circa 1958-1968).  One of
them shows you how to make an electric motor out of six tacks, a cork
from a bottle, wire, and magnets.
-- 
Rahul Dhesi         UUCP:  <backbones>!{iuvax,pur-ee}!bsu-cs!dhesi
                    ARPA:  dhesi@bsu-cs.bsu.edu

depolo@eniac.seas.upenn.edu (Jeff DePolo) (03/20/89)

In article <6237@bsu-cs.UUCP> dhesi@bsu-cs.UUCP (Rahul Dhesi) writes:
>In article <9916@bloom-beacon.MIT.EDU> yphotons@athena.mit.edu writes:
>>Have any ideas??????
>[about making a DC electric motor out of magnets, paper clips,
>thumbtacks, wire, and wood]
>
>Check the early issues of Popular Science (circa 1958-1968).  One of
>them shows you how to make an electric motor out of six tacks, a cork
>from a bottle, wire, and magnets.
>-- 
>Rahul Dhesi         UUCP:  <backbones>!{iuvax,pur-ee}!bsu-cs!dhesi
>                    ARPA:  dhesi@bsu-cs.bsu.edu

This sounds like my final project in highschool physics.  All we got was
some varnished wire, a 6V dry cell, a cork, paper clips, and a metal
rod to use as an axel.  We had to get it to run for 30 seconds straight
in order to pass.  No instruction was given.  Pretty good idea for a
practical test of physics skill/knowledge.  Note that that wasn't the
whole final.  Nothing could be THAT easy  :-)

						--- Jeff


+----------------------------------------------+------------------------------+
|  Jeff DePolo  [depolo@eniac.seas.upenn.edu]  | o  The best things in life   |
|   =>  The University of Pennsylvania  <=     |    come in six-packs.        |
| Class of 1991 - Computer Science Engineering | o  Life begins at 85 MPH.    |
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carl@aoa.UUCP (Carl Witthoft) (03/30/89)

In article <9916@bloom-beacon.MIT.EDU> yphotons@athena.mit.edu writes:
>Have any ideas??????
>
>A recent MIT physics (freshman) extra-credit problem: Given 2 small
>rectangular magnets, 2 paper clips, 2 thumb tacks, approx. 5 feet of
>wire, a small block of wood (4"X2"X.5") build a DC motor running of 1
>1.5V that can at least reach 2600 rpm. The use of glue, tape, etc in
>the final product will disqualify you. Only the above mentioned items
>can be in the final product. The use of a drill, saw, etc.  in
>building the motor is ok.

This is clearly a blatant attempt to get net physics gurus to help
this student cheat in class :=).  I propose :=) we only allow 
responses from other students in the same class.


-- 

Alix' Dad ( Carl Witthoft @ Adaptive Optics Associates)
" Axis-navigo, ergo sum."
{harvard,ima}!bbn!aoa!carl
54 CambridgePark Drive, Cambridge,MA 02140 617-864-0201
"disclaimer? I'm not a doctor, but I do have a Master's Degree in Science!"

bobp@sfsup.UUCP (+Phillips R.) (04/01/89)

In article <746@aoa.UUCP>, carl@aoa.UUCP (Carl Witthoft) writes:
> In article <9916@bloom-beacon.MIT.EDU> yphotons@athena.mit.edu writes:
> >Have any ideas??????
> >
> >A recent MIT physics (freshman) extra-credit problem: Given 2 small
> >rectangular magnets, 2 paper clips, 2 thumb tacks, approx. 5 feet of
> >wire, a small block of wood (4"X2"X.5") build a DC motor running of 1
> >1.5V that can at least reach 2600 rpm. The use of glue, tape, etc in
> >the final product will disqualify you. Only the above mentioned items
> >can be in the final product. The use of a drill, saw, etc.  in
> >building the motor is ok.
> 
> This is clearly a blatant attempt to get net physics gurus to help
> this student cheat in class :=).  
> Alix' Dad ( Carl Witthoft @ Adaptive Optics Associates)

If it is an attempt to cheat, it is a horribly feeble one.  I took this class
(mumblety-mumble years ago) and there is no real trick to getting the motor
going.  2600 rpm is easily attained.  Besides, when I took it, a student's
motor beat the crap out of the prof's.  
To the original poster, if Walter Lewin is still teaching that class, enjoy it;
it is the BEST class in the entire physics sequence (or, at least, it was once
upon a time).

Rob Phillips
Real World

blackje@sunspot.steinmetz (Emmett Black) (04/12/89)

>In article <746@aoa.UUCP>, carl@aoa.UUCP (Carl Witthoft) writes:
>> This is clearly a blatant attempt to get net physics gurus to help
>> this student cheat in class :=).  

Let's not forget that MIT teaches people to be ENGINEERS;
and good Engineers should make the most effective use of the
resources available to them.
The student in question will certainly not get a COMPLETE answer
from the net; and the net will certainly not build the motor.
However, a clue or a reference might be obtained to set a creative
developing engineer's mind at work to seize a better solution!
The query to the net is therefore not unlike seeking a reference
in an encyclopedia -- or other references in the library...

Remember the law school fable of the professor who gave an impossibly
large assignment?  No single student, or even a study group had a prayer
of completing it.  The study groups agreed to exchange parts of the 
assignment;  and drew up contracts with each other to protect themselves.
The course was "contracts" and the content of the assignment had nothing
whatever to do with the lesson being taught.

--Emmett
	J.E.Black; GE Research/K1-3C26; Schenectady, NY 12345
	blackje@crd.ge.com;   ...!uunet!steinmetz!crd!blackje