motorgliders as towplanes

On 20 Mar, 01:00, Bob Cook wrote:
Ian,

I was trying to point out a misconception that the "horizontal component
of lift" in a turn is somehow balanced by some other force.

If it were, the glider would not turn.

It all depends on your reference frame. To someone on the ground, an
unbalanced sideways force gives rise to the necessary acceleration.
But to an observer moving with the glider - the pilot, say - there is
no sideways acceleration /of the glider/ (the rest of the world may,
of course, be doing something). To the moving observer, an equal an
opposite centrifugal force provides the necessary balance.

We engineers like modelling with moving reference frames and
centrifugal forces because it turns dynamics problems into statics
problems, which are generally simpler. Physicists, and particularly
school physics teachers, traditionally get terribly upset by the idea
of centrifugal force.

Ian

On Mar 20, 1:32 am, The Real Doctor wrote:

Physicists, and particularly
school physics teachers, traditionally get terribly upset by the idea
of centrifugal force.

Ian

Physicsists make equally snarky comments about engineers, Ian. My
engineering dynamics professor at UC, Berkeley was adamant in
opposing the perpetuation of the centrifugal force myth. It's phony
physics and can lead to seriously erroneous conclusions.

Myles

On 21 Mar, 05:21, Myles wrote:
On Mar 20, 1:32 am, The Real Doctor wrote:

Physicists, and particularly
school physics teachers, traditionally get terribly upset by the idea
of centrifugal force.

Physicsists make equally snarky comments about engineers, Ian. *

Indeed. Bu hey, the mathematicians despise us all.

My
engineering dynamics professor at UC, Berkeley was *adamant in
opposing the perpetuation of the centrifugal force myth. *It's phony
physics and can lead to seriously erroneous conclusions.

It's a perfectly useful tool if applied correctly. That normally means
within a moving axis system, and getting there is not always simple.
You always have to decide whether it's going to be easier overall to
use the difficult model with the simple setup (stationary axes) or the
simple model with the difficult setup (moving axes).

It's the same in fluids - normally we model a glider by holding it
still and letting the air move past, but that's not always the best
way, or the easiest way. Mind you, I'm a typical lazy engineer, so for
me best = easiest in about 99% of cases.

Ian

Myles wrote:
On Mar 20, 1:32 am, The Real Doctor wrote:

... My engineering dynamics professor at UC, Berkeley was adamant in
opposing the perpetuation of the centrifugal force myth. It's phony
physics and can lead to seriously erroneous conclusions.

Yeah, yeah, centrifugal force is a reaction to a centripetal force, I
know the difference,.... I don't care. The layman understands the former
term and not the latter. To the typical student, I'll use the term
"centrifugal". If he's a physicist, I'll say "centripetal". :-)

Tony V.