baloon static in air

udit wrote:

i have another question
suppose a hot air ballon is made still in mid air.
then the earth will rotate under it
so will the baloon reach from one one place to another standing at one
place? answer required.

No. A balloon is always (mostly) stationary with respect to the airmass that
it is in. With respect to the ground it goes whereever the wind goes.

The only time it's not stationary in the airmass is when something is
dragging on the ground (as at launch or landing) or when it is passing
through a windshear.

Keith Harwood wrote:
udit wrote:

i have another question
suppose a hot air ballon is made still in mid air.
then the earth will rotate under it
so will the baloon reach from one one place to another standing at one
place? answer required.

No. A balloon is always (mostly) stationary with respect to the airmass that
it is in. With respect to the ground it goes whereever the wind goes.

The only time it's not stationary in the airmass is when something is
dragging on the ground (as at launch or landing) or when it is passing
through a windshear.

Or when wind direction changes.

Keith Harwood wrote:

udit wrote:

i have another question
suppose a hot air ballon is made still in mid air.
then the earth will rotate under it
so will the baloon reach from one one place to another standing at
one place? answer required.

No. A balloon is always (mostly) stationary with respect to the
airmass that it is in. With respect to the ground it goes whereever
the wind goes.

The only time it's not stationary in the airmass is when something is
dragging on the ground (as at launch or landing) or when it is passing
through a windshear.

So on moon, if we do same stunt and get up to 10m in space the land
will move below

--
-Gk

Ian Stirling wrote:

Keith Harwood wrote:

The only time it's not stationary in the airmass is when something is
dragging on the ground (as at launch or landing) or when it is passing
through a windshear.

Or when wind direction changes.

Yup, but it's only momentary. The force arising from the wind change is
applied over the whole crosssection of the ballon and is enormous compared
to the mass of the balloon. From F=ma, the acceleration a must be very
large. If the change in velocity of the wind is v then the time t to change
the velocity of the balloon is given by v=at. v is small, a is enormous, t
is terribly small. But the rate of change of the wind isn't all that crash
hot, so if t is terribly small then v must be terribly small. If you do
this properly using the rate of change of wind velocity to calculate F
you'll find that to all intents and purposes the balloon is embedded in the
air mass regardless of changes in the wind.

Dave wrote:

"George Kinley" wrote in message
...

So on moon, if we do same stunt and get up to 10m in space the land
will move below

--
-Gk

Aaah, but there's the rub...with no atmosphere, there's no medium in which
a balloon can be buoyant, so you can't remain aloft.

And with no air there's no wind, so the land won't move. It's the wind which
makes the balloon move with respect to the ground.

Ian Stirling wrote:

Keith Harwood wrote:
Dave wrote:

"George Kinley" wrote in message
...

So on moon, if we do same stunt and get up to 10m in space the land
will move below

Aaah, but there's the rub...with no atmosphere, there's no medium in
which a balloon can be buoyant, so you can't remain aloft.

And with no air there's no wind, so the land won't move. It's the wind
which makes the balloon move with respect to the ground.

Well, with no air, the coefficient of friction to the ground is
significantly higher.

Ah, very true.

But getting back to the original premise, it seems from a few discussions
around here that there are people who think that if you are attached to a
moving body and suddenly become unattached, that you stop moving. This idea
was debunked three and a half centuries ago. Why does it still persist?

udit wrote:

i have another question
suppose a hot air ballon is made still in mid air.
then the earth will rotate under it
so will the baloon reach from one one place to another standing at one place?
answer required.


Before I read the other responses I have one question:

How coupled to the rotating planet is the atmosphere the balloon is
floating in?

Seems the rotating planet isn't as much a concern as how fast the wind
is blowing.


TBerk

But if the coefficient of friction to the ground is significantly
higher then... uhh... I dunno.