[Phys-L] Re: Newton's Equation - 2 or 3 terms?

[Bernard Cleyet <anngeorg@PACBELL.NET>]

depends

If the burning area increases, e.g. from the cross section to conical,
the F increases.  It will then decrease as the initial burning part
exhausts. Whatever, the mass decreases and not at a constant rate.  The
early cruise (V 1) and the ballistic (V 2)  missiles,  I assume, used
pressure feed  (liquid fuel), in which case the force decreased as the
fuel exhausted.  What ever happens, w/ modern tech. the computer will
compensate.

Trivium:  the clock to shut off some of the engines' fuel (over London)
was an electrolytic cell.  Another was a log (like the naval one).

bc, by a stroke of fortune (?) missed the excitement of buzz bombs.


Anthony Lapinski wrote:

> I may be mistaken, but don't rockets have a constant thrust (F)? As the
> fuel (m) burns off,
> the acceleration (a) actually increases.
>
> Forum for Physics Educators <PHYS-L@list1.ucc.nau.edu> on Monday,
> September 5, 2005 at 11:48 AM -0500 wrote:
>
> > You mean the cart's mass is leaking out the bottom, or the conveyer
> > problem (mass added to the belt)?  Better are rocket problems especially
> > as the fuel runs out varying the F as well as the M.
> >
> > bc, still no deluge?
> >
> > P.s. wasn't it originally stated as F = p ^.   ?  So (accidentally) GR
> > compatible?
> >
> > Ludwik Kowalski wrote:
> >
> >
> > > On Monday, Sep 5, 2005, at 09:36 America/New_York, Brian Whatcott wrote:
> > >
> > >
> > >
> > > > At 06:40 AM 9/5/2005, Gene Mosca, you wrote:
> > > >
> > > >
> > > >
> > > > > On September 4, 2005 3:44:21 PM EDT, John Clement wrote:
> > > > >
> > > > >
> > > > >
> > > > > > 3 variable equations such as F=ma
> > > > >
> > > > > F=ma is a two variable equation.  Mass is not a variable in this
> > > > > equation
> > > > >
> > > > > Gene
> > > >
> > > >
> > > > In the variant f = mg we suppose that the force acting is
> > > > proportional to the mass, in order to justify the constant
> > > > acceleration due to gravity.
> > >
> > >
> > > Mass is also a variable in a setup with which the effect of the mass on
> > > acceleration (keeping F constant) is demonstrated.
> > > What I have in mind is a loaded cart (variable m1) accelerated along
> > > the horizontal surface by a net force F=(m2-m1)*g, where m2 is a mass
> > > suspended over a pulley. It is a good and effective demo.
> > >
> > > Ludwik Kowalski
> > > Let the perfect not be the enemy of the good.
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