Possibly incredibly stupid question about gravity in an aeroplane

[jessb]

I just want to make absolutely sure, but does anyone know if you actually do weigh less in a plane, and if you do, is it measurable?

Obviously a flying aeroplane, and not one on the ground ;)

Thanks! Jess

 

[ZapperZ]

I just want to make absolutely sure, but does anyone know if you actually do weigh less in a plane, and if you do, is it measurable?

Obviously a flying aeroplane, and not one on the ground ;)

Thanks! Jess

You already weigh less when you are high up in the mountains. That's why places such as Denver, CO, and other cities up in the mountains have "thinner air".

Since an airplane travels higher than even these mountains, you can draw your own conclusion from there.

Zz.

 

[rewebster]

except maybe on take off and in curves

 

[Hootenanny]

except maybe on take off and in curves

Your weight would still not change. Weight is a function of distance only, nothing else. Your apparent weight may change, i.e. the magnitude of the normal force from your seat.

 

[jessb]

You already weigh less when you are high up in the mountains. That's why places such as Denver, CO, and other cities up in the mountains have "thinner air".

Since an airplane travels higher than even these mountains, you can draw your own conclusion from there.

Zz.

I guessed as much... but is it measurable? (on regular scales like you would have in your bathroom)

 

[rewebster]

Your weight would still not change. Weight is a function of distance only, nothing else. Your apparent weight may change, i.e. the magnitude of the normal force from your seat.

it seems to me, it would be when (a moment in time) and where (an exact location/circumstance in that moment of time) when you would weigh yourself (weigh less)---wouldn't you weigh less on the moon?

 

[jessb]

it seems to me, it would be when (a moment in time) and where (an exact location/circumstance in that moment of time) when you would weigh yourself (weigh less)---wouldn't you weigh less on the moon?

I think what he was saying was that the pull of the Earth on your body would still be the same in the plane if it was doing a parabolic flight and you appeared weightless, or if it was a regular flight and you didn't, so long as you were at the same distance from earth?

 

[lpfr]

You already weigh less when you are high up in the mountains. That's why places such as Denver, CO, and other cities up in the mountains have "thinner air".
Zz.

You weight less as you climb. But this is not the reason why the atmospheric pressure diminishes with height.
Atmospheric depends on the weight of the air column from de place you are until free space.
Although gravity diminishes with height, it does so far much slowly than atmospheric pressure.
As an example, in the summit of the Everest, gravity is only 0.25% lower than at sea level, but atmospheric pressure is just 35% of sea level pressure.

 

[AlephZero]

I guessed as much... but is it measurable? (on regular scales like you would have in your bathroom)

Earth radius = 6400 Km (approx).
Typical cruise height of civil aircraft = 35,000 ft = 11 Km.

Change in gravitational attraction (a.k.a. weight) = (6400/6411)^2 = 0.996

A 0.4% change isn't hard to detect.

 

[ZapperZ]

I guessed as much... but is it measurable? (on regular scales like you would have in your bathroom)

It might, depending on how good your bathroom scale is (mine reads up to 1 decimal place).

The approximate difference in g between Denver, CO and sea level is about 0.06%. So for a 150 lb person, the change is weight between the two is about 0.1 lb. So yes, you can detect this with a bathroom scale.

Zz.

 

[rewebster]

OK--if that's what your specific circumstance was in your original question

 

[jessb]

It might, depending on how good your bathroom scale is (mine reads up to 1 decimal place).

The approximate difference in g between Denver, CO and sea level is about 0.06%. So for a 150 lb person, the change is weight between the two is about 0.1 lb. So yes, you can detect this with a bathroom scale.

Zz.

Thanks! That's really helpful :D

Jess

 

[Hootenanny]

it seems to me, it would be when (a moment in time) and where (an exact location/circumstance in that moment of time) when you would weigh yourself (weigh less)---wouldn't you weigh less on the moon?

You would indeed weight less on the moon, but how many aeroplanes fly on the moon...

 

[rewebster]

You would indeed weight less on the moon, but how many aeroplanes fly on the moon...

well since there's no aer on the moon---not many I would guess---

just nailing down the specific circumstance.

----------
If I'm not mistaken though, if you had the scale on the plane with you, and weighed yourself---I believe you'd weigh the same as if you weren't on the plane (on earth) and weighing yourself--I think it would depend on what type of scale you were using too.