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russ(at)rkiphoto.com
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 Posted: Thu Jan 24, 2008 7:03 am Post subject: speeds |
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Seems I've recently read an awful lot of semi-conflicting things
about speed, acceleration, etc.
Well FWIW, unless they've changed things since my student days,
acceleration is a CHANGE in velocity. A car doing a steady 60MPH
down the highway has NO acceleration. If the speed is changed, it
accelerates or decelerates.
An aircraft in steady cruise flight has NO acceleration or
deceleration unless its speed is changed.
Sure seem to be an awful lot of experts out there.
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Rex Rodebush
Joined: 10 Jan 2006
Posts: 209
Location: Branson West area, Missouri
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| Posted: Thu Jan 24, 2008 10:21 am Post subject: Re: speeds |
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Russ,
You are correct if the car is going in a straight line. If you take a sharp corner keeping your speed the same you will feel side acceleration g's.
You will feel g's if you slow down, go faster, or just change directions. Ask the guy who is feeling 6 g's in an Air Force centirfuge. His speed is the same but he is constantly changing directions.
Rex Rodebush
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Thu Jan 24, 2008 10:22 am Post subject: speeds |
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At 09:57 AM 1/24/2008, Russ Kinne wrote:
| Quote: | --> Kolb-List message posted by: Russ Kinne <russ(at)rkiphoto.com>
Seems I've recently read an awful lot of semi-conflicting things
about speed, acceleration, etc.
Well FWIW, unless they've changed things since my student days,
acceleration is a CHANGE in velocity. A car doing a steady 60MPH
down the highway has NO acceleration. If the speed is changed, it
accelerates or decelerates.
An aircraft in steady cruise flight has NO acceleration or
deceleration unless its speed is changed. |
An object (e.g. an aircraft) traveling in a curve at a constant speed is experiencing acceleration at 90° to its direction of travel at any moment.
Acceleration IS a change in velocity, since velocity is a vector quantity, defined as speed in a certain direction. Speed is a scalar quantity, which doesn't include a direction vector. So technically in a turn, the velocity changes while the speed stays constant.
-Dana
--
When you were born, you cried and the world rejoiced...
Live your life so that when you die, the world cries and you rejoice.
-- Cherokee saying [quote][b]
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jbhart(at)onlyinternet.ne
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| Posted: Thu Jan 24, 2008 11:07 am Post subject: speeds |
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From: Dana Hague <d-m-hague(at)comcast.net>
| Quote: | >>>>>>>>>>>>>>>>>
An object (e.g. an aircraft) traveling in a curve at a constant speed is
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experiencing acceleration at 90° to its direction of travel at any
moment.
Acceleration IS a change in velocity, since velocity is a vector quantity,
defined as speed in a certain direction. Speed is a scalar quantity, which
doesn't include a direction vector. So technically in a turn, the velocity
changes while the speed stays constant.
| Quote: | >>>>>>>>>>>>>>>>>>>>
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Dana,
This only so if your reference point is on the ground.
But if your reference point is in the plane, it is the earth that is
accelerating. This is why John's G meter read 1g over a constant speed
flight path. The G meter could care less about what the earth was doing or
the G meter's relation ship to the earth. It only reads what is being
experienced by the aircraft. In this case the velocity vector is in a
constant magnitude and direction relative to the aircraft, therefore the G
meter reads a constant value and the wing experiences a constant load. This
goes to support the fact that if you fly at constant speed/velocity that is
best glide, there is no danger of stalling for tearing the wings off the
plane. The pilot still bears the responsibility of not decelerating too
rapidly upon touch down.
This has been a fun subject to help combat the weather.
Jack B. Hart FF004
Winchester, IN
do not archive
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Steve Boetto
Joined: 11 Jan 2006
Posts: 364
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| Posted: Thu Jan 24, 2008 11:43 am Post subject: speeds |
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All of this Nuts and Bolts, facts and figures are interesting however, if I take my little Firefly out and stick his little nose towards the ground, wring him out with a bunch of bank and pull back on the stick the results are not only fun but very effective in changing direction and losing altitude with very little gain in the weight I feel in my seat. It is nice to know why this happens by the numbers but I suggest that you go out and try it.
In a message dated 1/24/2008 2:08:25 P.M. Eastern Standard Time, jbhart(at)onlyinternet.net writes:
| Quote: |
From: Dana Hague <d-m-hague(at)comcast.net>
| Quote: | >>>>>>>>>>>>>>>>>
An object (e.g. an aircraft) traveling in a curve at a constant speed is
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experiencing acceleration at 90° to its direction of travel at any
moment.
Steve
Firefly 007/Floats
do not archive
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Start the year off right. Easy ways to stay in shape in the new year.
[quote][b]
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Dana
Joined: 13 Dec 2007
Posts: 1047
Location: Connecticut, USA
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| Posted: Thu Jan 24, 2008 6:08 pm Post subject: speeds |
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At 02:09 PM 1/24/2008, Jack B. Hart wrote:
| Quote: | This only so if your reference point is on the ground.
But if your reference point is in the plane, it is the earth that is
accelerating. This is why John's G meter read 1g over a constant speed
flight path. The G meter could care less about what the earth was doing or
the G meter's relation ship to the earth.
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It doesn't matter what your reference point is, you can't ignore the Earth,
since the aircraft is being attracted to it by gravity. That force is part
of the vector sum of forces on the aircraft, which must equal zero or else
the aircraft accelerates in the direction of the imbalance-- downward and
inward in the case of coordinated 1g banked turn.
The laws of physics don't vary, but experimental error does.
-Dana
--
The gene pool has no lifeguard.
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pj.ladd(at)btinternet.com
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| Posted: Fri Jan 25, 2008 3:25 am Post subject: speeds |
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Hi,
all this talk about gravity and `G` forces reminds me of a one liner someone sent to me recently.
`The World may suck, but if it didn`t we would all fly off``
Cheers
Pat
[quote][b]
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a58r(at)verizon.net
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| Posted: Fri Jan 25, 2008 10:21 am Post subject: speeds |
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Pat, Corollary: There's no such thing as Gravity; the Earth sucks.
regards,
Bob N. FireFly 070 Old Kolb
http://www.angelfire.com/rpg/ronoy/
do not archive
[quote][b]
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pj.ladd(at)btinternet.com
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| Posted: Sat Jan 26, 2008 3:05 am Post subject: speeds |
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the Earth sucks.>>
Hi Bob,
I did hear that helicopters don`t really fly. They are just so damned ugly that the Earth repels them.
Cheers
Pat
[quote][b]
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