I don't think Rick's suggestion is a bad one. However, I would like a
special symbol for the free-fall acceleration.
Perhaps using a_g for that would satisfy that criteria allowing me to
use the m/s^2 for that and then when I get to NII, I'd use F_g=m*g where
the units of g are N/kg and therefore be able to follow RT's suggestion
below as well.
________________________
Joel Rauber
Department of Physics - SDSU
Joel.Rauber@sdstate.edu
605-688-4293
| -----Original Message-----
| From: phys-l-bounces@carnot.physics.buffalo.edu
| [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf
| Of Rick Tarara
| Sent: Monday, September 17, 2007 9:44 AM
| To: Forum for Physics Educators
| Subject: Re: [Phys-l] PER folks and units of g
|
| I would think the problem here would go away if nobody used
| 'g' as the acceleration due to gravity. When we do
| kinematics, I don't allow equations that start out with a 'g'
| in them. Rather we identify the acceleration (a) as about 10
| m/s^2 down. The only loss (and I don't consider it large)
| would be that we shouldn't really use the Range equation R =
| (v^2)sin92theta)/g -- but with it's use so limited, I try to
| avoid it in favor of working out any 2-D motion from first principles.
|
| OTOH, we could also reserve 'g' as the acceleration due to
| gravity (with acceleration units), and always use script-G
| for the gravitational field.
| But that would require we write Weight = mG rather than mg.
|
| So--use 'g' only as the field (N/kg) or only as an acceleration.
|
| Rick
|
| ----- Original Message -----
| From: "Ken Fox" <physicsfox23@gmail.com>
| To: "Forum for Physics Educators" <phys-l@carnot.physics.buffalo.edu>
| Sent: Monday, September 17, 2007 10:15 AM
| Subject: Re: [Phys-l] PER folks and units of g
|
|
| >I agree with Jeffrey's as the best solution. In my mind
| there is a huge
| > conceptual difference between a(g) and g. It is a wonderful
| point of
| > nature
| > that they are numerically equal and even the units are
| equivalent (pun
| > intended). I tweak the brain by indicating that one day they will
| > appreciate
| > this coincidence.
| >
| > ma(g) = mg two concepts of mass are at work here as well.
| >
| > One hard thing about this is conflicting with the text book or web
| > resources.
| >
| > Ken Fox
| >
| > On 9/17/07, Jeffrey Schnick <JSchnick@anselm.edu> wrote:
| >>
| >> I use a_g = 9.8 m/s^2 for the acceleration of an object in
| freefall near
| >> the surface of the earth and g = 9.8 N/kg for the magnitude of the
| >> earth's near-surface gravitational field.
| >>
| >> > -----Original Message-----
| >> > From: phys-l-bounces@carnot.physics.buffalo.edu
| >> > [mailto:phys-l-bounces@carnot.physics.buffalo.edu] On Behalf
| >> > Of Rauber, Joel
| >> > Sent: Monday, September 17, 2007 9:34 AM
| >> > To: phys-l@carnot.physics.buffalo.edu
| >> > Subject: [Phys-l] PER folks and units of g
| >> >
| >> > This is mostly addressed to the PER gurus, but others should
| >> > need no invitation to chime in, as their experience is
| >> > appreciated and valuable.
| >> >
| >> > There was a post a while back that suggested that the PER
| >> > research was indicating that it is best to quote g as follows:
| >> >
| >> > g = 9.8 N/kg rather than g = 9.8 m/s^2
| >> >
| >> >
| >> > the question I have is following a traditional sequence of
| >> > kinematics first, while introducing free-fall what do you
| >> > suggest for g?
| >> >
| >> ...
| >> _______________________________________________
| >> Forum for Physics Educators
| >> Phys-l@carnot.physics.buffalo.edu
| >> https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
| >>
| > _______________________________________________
| > Forum for Physics Educators
| > Phys-l@carnot.physics.buffalo.edu
| > https://carnot.physics.buffalo.edu/mailman/listinfo/phys-l
| >
|
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