Date: Wed Nov 29 13:01:49 2006 Back to Contents

Author: Samuel M Sampere

Subject: Re: Finding force on a launched 2-liter bottle

Post:
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Suppose I asked you to hold your hand over the opening of the bottle
while I pumped it up. What force would you have to exert over a small
opening? Over a larger opening? Over the nozzle?=20

=20

Ok, now it's capped. Consider the layer of air just inside the cap? What
pressure does it feel? What is the total force exerted on the cap?=20

=20

I get 115 PSI*CA.

=20

If that's exerted on the cap, then N3 says that the same force is
exerted on the bottle and it's contents.

=20

As others have pointed out, this is only the force at that instant.=20

=20

Build a jig to hold the bottle, position a force sensor opposite the
nozzle, and let 'er rip. If you trigger this right, you ought to get a
decent F-t curve. That sounds like a fun experiment.

=20

Sam

=20

________________________________

From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Richard Heckathorn
Sent: Wednesday, November 29, 2006 12:24 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] Finding force on a launched 2-liter bottle=20

=20

Greetings

=20

If it's pumped to 115 PSI, then the force at release is 115*cross
sectional area of the bottle opening, ballpark .5 ~ .75 in^2.

=20

The product of the PSI and the area of the opening would be the force on
the bottle? My thinking says no. I would think the is the force or an
equivalent area of the bottle as well. But what is the area of the
bottle that this force is acting on?

=20

Now am I missing something?

=20

Dick

=20

Helping teachers who facilitate, motivating students who learn.

Dick Heckathorn 14665 Pawnee Trail Middleburg Hts, OH 44130
440-826-0834

www.cvcaroyals.org/~rheckathorn/

Adjunct Physics Teacher - Baldwin Wallace College

Physics is learning how to communicate with ones environment so that it
will talk back.

=20

=20

-----Original Message-----
From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On
Behalf Of Samuel M Sampere
Sent: Wednesday, November 29, 2006 1:20 AM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] Finding force on a launched 2-liter bottle=20

=20

If it's pumped to 115 PSI, then the force at release is 115*cross

sectional area of the bottle opening, ballpark .5 ~ .75 in^2.=20

=20

What he really wants, I think, is an F-t graph.=20

=20

Sam

=20

-----Original Message-----

From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On

Behalf Of Richard Heckathorn

Sent: Wednesday, November 29, 2006 12:38 AM

To: tap-l@lists.ncsu.edu

Subject: [tap-l] Finding force on a launched 2-liter bottle=20

=20

Greetings,

=20

A friend of mine (middle school teacher) has his

student launch 2-liter bottle rockets. He stated:

=20

"This years best flew 200meters had a mass of

300grams and was launched at a 45 degree angle @

115 PSI"

=20

"Is there a way I can find the amount of "force"

on the bottle?"

=20

=20

The only way I thought of was:

=20

Find the mass of the bottle and water. Measure the

velocity of the bottle and water(if any) after

launch. Divide the estimated time for this to take

place into the change in momentum to get the

approximate force.

=20

Since water is leaving the bottle, one would need

to gestimate the average mass.

=20

Your thoughts?

=20

Dick

=20

Helping teachers who facilitate, motivating

students who learn.

Dick Heckathorn 14665 Pawnee Trail Middleburg

Hts, OH 44130 440-826-0834

www.cvcaroyals.org/~rheckathorn/

Adjunct Physics Teacher - Baldwin Wallace College

Physics is learning how to communicate with ones

environment so that it will talk back.

=20

=20

-----Original Message-----

From: tap-l-owner@lists.ncsu.edu

[mailto:tap-l-owner@lists.ncsu.edu] On Behalf Of

Doug Welch

Sent: Monday, November 27, 2006 3:06 PM

To: tap-l@lists.ncsu.edu

Subject: Re: [tap-l] temperature sensor where to

buy?

=20

=20

Paul,

=20

Here is another source of even cheaper devices.

I've used one of their=20

earlier models.

*

***PE Mini at US$15 each at

http://www.tempgun.com/specs.html

=20

Cheers,

Doug

=20

Paul Doherty wrote:

> I'm looking for some inexpensive temperature

sensors the kind you=20

> point at an object and it reads the temperature.

> Got any suggestions?

>=20

> (These are for student use so they don't have to

be precision=20

> instruments)

>=20

> Paul D

>=20

=20

=20

=20

=20

=20


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Suppose I asked you to hold your =
hand over
the opening of the bottle while I pumped it up. What force would you =
have to
exert over a small opening? Over a larger opening? Over the nozzle? =




Ok, now itís capped. Consider =
the
layer of air just inside the cap? What pressure does it feel? What is =
the total
force exerted on the cap?



I get 115 =
PSI*CA.



If thatís exerted on the cap, =
then
N3 says that the same force is exerted on the bottle and itís =
contents.



As others have pointed out, this is =
only
the force at that instant.



Build a jig to hold the bottle, =
position a
force sensor opposite the nozzle, and let Ďer rip. If you trigger =
this
right, you ought to get a decent F-t curve. That sounds like a fun =
experiment.



Sam











From:
tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On Behalf Of Richard =
Heckathorn
Sent: Wednesday, November =
29, 2006
12:24 PM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] =
Finding force
on a launched 2-liter bottle





Greetings



If it's pumped to 115 PSI, then the force at =
release
is 115*cross sectional area of the bottle opening, ballpark .5 ~ .75 =
in^2.



The product of the PSI and the area of the opening would be the =
force
on the bottle? My thinking says no. I would think the is the force or an
equivalent area of the bottle as well. But what is the area of the =
bottle that
this force is acting on?



Now am I missing something?



Dick



Helping teachers who facilitate, motivating students who =
learn.

Dick Heckathorn 14665 Pawnee Trail Middleburg =
Hts, OH
44130
440-826-0834

www.cvcaroyals.org/~rheckathorn/

Adjunct Physics Teacher - Baldwin
Wallace College<=
/p>

Physics is learning how to communicate with ones environment so =
that it
will talk back.





-----Original Message-----
From: tap-l-owner@lists.ncsu.edu [mailto:tap-l-owner@lists.ncsu.edu] On =
Behalf
Of Samuel M Sampere
Sent: Wednesday, November 29, 2006 1:20 AM
To: tap-l@lists.ncsu.edu
Subject: Re: [tap-l] Finding force on a launched 2-liter bottle =




If it's pumped to 115 PSI, then the force at release is =
115*cross

sectional area of the bottle opening, ballpark .5 ~ .75 in^2. =




What he really wants, I think, is an F-t graph. =




Sam



-----Original Message-----

From: tap-l-owner@lists.ncsu.edu =
[mailto:tap-l-owner@lists.ncsu.edu] On

Behalf Of Richard Heckathorn

Sent: Wednesday, November 29, 2006 12:38 =
AM

To: tap-l@lists.ncsu.edu

Subject: [tap-l] Finding force on a launched 2-liter bottle =




Greetings,



A friend of mine (middle school teacher) has =
his

student launch 2-liter bottle rockets. He =
stated:



"This years best flew 200meters had a mass =
of

300grams and was launched at a 45 degree angle =
@

115 PSI"



"Is there a way I can find the amount of =
"force"

on the bottle?"





The only way I thought of was:



Find the mass of the bottle and water. Measure =
the

velocity of the bottle and water(if any) =
after

launch. Divide the estimated time for this to =
take

place into the change in momentum to get =
the

approximate force.



Since water is leaving the bottle, one would =
need

to gestimate the average mass.



Your thoughts?



Dick



Helping teachers who facilitate, =
motivating

students who learn.

Dick Heckathorn 14665 Pawnee Trail =
Middleburg

Hts,
OH 44130
440-826-0834

www.cvcaroyals.org/~rheckathorn/

Adjunct Physics Teacher - Baldwin
Wallace College<=
/p>

Physics is learning how to communicate with =
ones

environment so that it will talk =
back.





-----Original Message-----

From: tap-l-owner@lists.ncsu.edu

[mailto:tap-l-owner@lists.ncsu.edu] On Behalf =
Of

Doug Welch

Sent: Monday, November 27, 2006 3:06 =
PM

To: tap-l@lists.ncsu.edu

Subject: Re: [tap-l] temperature sensor where =
to

buy?





Paul,



Here is another source of even cheaper =
devices.

I've used one of their

earlier models.

*

***PE Mini at US$15 each at

http://www.tempgun.com/specs.html



Cheers,

Doug



Paul Doherty wrote:

> I'm looking for some inexpensive =
temperature

sensors the kind you

> point at an object and it reads the =
temperature.

> Got any suggestions?

>

> (These are for student use so they don't have =
to

be precision

> instruments)

>

> Paul D

>

















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