# if my calculations are correct.....

Posted:
edited January 2014
SLINKY + ESCULATOR = EVERLASTING FUN
«1

Posts: 626member
Timing is everything.....
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the escalator would have to be moving at a pretty good clip...
Posts: 123member
until the nasty horrible death when the slinky got jammed in the cracks in the escalator. Has anyone ever stretched a slingy out straight? How Long?
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2*pi*r*L where r is the radius of the coil and L is the number of stacked coils.
Posts: 123member
Quote:

Originally posted by Scott

2*pi*r*L where r is the radius of the coil and L is the number of stacked coils.

That is clearly wrong, because you havn't allowed for the fact that each coil is not planar. Try again.
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I'm sure it's close enough Calcualte how much extra lenght you'ld need of the offset were the width of the wire.
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I like the concept, but I fear that the escalator would likely eat the slinky, unless you were superb with your slinky skills.

didn't I already respond to this thread when it first dropped? guess not \

Another thing I'd like to do is ride a wheeled something(bicycle, skateboard, scooter, unicycle) on one of those horizontal escalator dealies at airports.
Posts: 4,841member
Quote:

Originally posted by powermacG6

That is clearly wrong, because you havn't allowed for the fact that each coil is not planar. Try again.

Clearly there is also the issue that unless you are heating the coil it will never be straight...
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Here's an alternative method.

Determine the mass m. Determine the cross sectional area of the wire, A. Knowing the density p.

L= m/Ap.

QED
Posts: 1,343member
Quote:

Originally posted by Wrong Robot

Another thing I'd like to do is ride a wheeled something(bicycle, skateboard, scooter, unicycle) on one of those horizontal escalator dealies at airports.

Hmm. I want to do that too! Great idea.
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given small enough wheels you might be able to stay vertical if you peddled just enough to break friction.
Posts: 4,695member
Quote:

Originally posted by Wrong Robot

Another thing I'd like to do is ride a wheeled something(bicycle, skateboard, scooter, unicycle) on one of those horizontal escalator dealies at airports.

The problem is you'd be tackled, beaten, arrested as a terrorist, thrown in jail, and give a full body cavity search while your bicycle was being x-rayed then sliced into tiny pieces in a search for explosives.

Not that there's anything particularly scary or threatening about a bicycle in an airport, but these guys just don't have much of a sense of humor anymore.
Posts: 123member
Quote:

Originally posted by Scott

Here's an alternative method.

Determine the mass m. Determine the cross sectional area of the wire, A. Knowing the density p.

L= m/Ap.

QED

That is clearly wrong!

You havn't allowed for the fact that density is dependant on temperature
Posts: 7,431member
Quote:

Originally posted by powermacG6

That is clearly wrong!

You havn't allowed for the fact that density is dependant on temperature

Trivial

L(T)=m/A(T)p(T)

QED
Posts: 123member
Posts: 4,841member
Quote:

Originally posted by Scott

Trivial

L(T)=m/A(T)p(T)

QED

Heh. Assuming that the thermal expansion of the material is the same in all directions, A(T)= p(T) (V(T1)*A(T1)/m) where the V(T1) and A(T1) are the volume and cross sectional area of the slinky at a given temperature T1, respectively.

This gives:

L(T)= m^2/(p(T)^2 *(V(T1)*A(T1)))

Of course this is assuming that the added mass energy from heating is negligible -- which as we know is an invalid assumption when discussing an infinitely long slinky, which we clearly are...
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Quote:

Originally posted by powermacG6

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Infinitely long? We're trying to estimate the length of a manufactured slinky.

Why don't we come to a consensus on the level of error we're willing to accept and that will help guide us on how complex our model needs to be? I think if we were within a centimeter that would be good.

I'll contact the manufacture to see of we can get several hundred for destructive testing.