Neil
I agree with you. I come back to what I said earlier. Pound/kg (being
both masses) is a fixed ratio, no matter what the gravitational pull
causing acceleration. An earth pound of sugar on the moon will feel ~1/6
as heavy and an earth kg of sugar on the moon will also feel ~1/6 as
heavy. Both, measured on an equilibrium balance, against standard
weights, will weigh what they did on earth but, on a spring balance,
will indicate ~1/6 the weight.
I agree with you that SI or, at least, derived metric units should be
the only units used for scientific and technological subjects. The USA
passed a metrication bill in, I think, 1886, making metric units the
standard. It just takes them a little time to put into practice what the
legislators say. As the USA signed the ISO papers standard about 40
years ago, it may mean that they will abandon their terrible letter and
legal sizes in another 100, who knows? I'm afraid that I shall never see
a US document fit comfortably into a file that you can buy in
practically any country of the world! :-(
Brian
Neil Atkinson wrote:
>
> I've forgotten what the original question was but I think we are getting
> confused between metric and imperial measures. Just for the record:
>
> In SI units (which we should all be using!!!),
>
> Mass = Kg
> Force = Newton
>
> In old Imperial Units:
> Mass = Pound or Ounce
> Force = Pound-Force or Ounce-Force
>
> See web site: http://physics.nist.gov/cuu/Units/units.html for a full list
> of SI units.
>
> I've just re-read the original question and the answer is no, you can't
> convert Kg or Ib to G force. G Force is dependant on the Mass. e.g. the
> force exerted on a racing drivers neck as he turns a corner will increase if
> his helmet is heavier. i.e. Mass (Kg) x Acceleration (M/s^2).
>
> 1G is equal to the force applied by the earth's gravity i.e. the force on a
> given mass due to an acceleration of 9.8M/S^2.
>
> I am not a physicist so if any of the above is incorrect I am sure someone
> will tell me.
>
> But please lets stick to one system of measure (preferably SI units).
>
> Neil
>
> -----Original Message-----
> From: Lou Hart [mailto:[log in to unmask]]
> Sent: 09 October 2001 21:51
> Subject: Re: Question for the physics "gurus"
>
> Jason sure has gotten a lot of feedback on this question. I have these
> comments.
>
> Pound/kilogram is, in principle, acceleration, since the pound is a unit of
> force, and force divided by mass is acceleration. According to a
> conversion calculator a colleague gave me, 1 pound (force) is 4.448222
> newtons. Since G= (approximately) 9.8 m/sec^2 (meters per second
> squared), it looks like (pound/kilogram) x 2 = G (approximately, as
> acceleration).
>
> Jason refers to G force. Mass x G = force (weight) as several have pointed
> out. A body's mass has a force (weight) applied to it when accelerated.
>
> I wonder if something is left out of the question - are these some kind of
> shorthand units? For example, in referring to flight, people talk about G
> force - since a pilot's mass does not change, acceleration will effectively
> add to weight force on the body. No matter the mass of the pilot's body,
> the multiplier increasing the force on it above that on the earth's surface
> is the acceleration (commonly expressing in "G"s). My favorite example of
> a shorthand unit is wave number, the number of wavelengths of radiation in
> 1 centimeter. I believe it is most commonly used in infrared spectroscopy
> as a unit of energy. "Inverse centimeters" seems far removed from energy,
> but is equivalent if you understand the shorthand involved and multiply
> wavenumber by Planck's constant and again by the speed of light.
>
> I look forward to the day when "pounds" and "inches" are as commonly used
> in mechanics as "statcoulombs" and "abamps" now are in electricity and
> magnetism. Lou Hart
>
> -----Original Message-----
> From: <Rudy Sedlak> [SMTP:[log in to unmask]]
> Sent: Tuesday, October 09, 2001 2:42 PM
> To: [log in to unmask]
> Subject: Re: [TN] Question for the physics "gurus"
>
> 1 "G" = 32 feet/second/second
>
> don't think you can convert kilos to feet/second/second
>
> Rudy Sedlak
> RD Chemical Company
>
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