As you move higher on earth do you weigh more?

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Discussion Overview

The discussion revolves around the question of whether a person's weight changes as they move to higher elevations on Earth. Participants explore the effects of gravity and buoyancy at different altitudes, considering both theoretical and practical implications.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions whether weight increases at higher altitudes, drawing an analogy to buoyancy in water.
  • Another participant asserts that weight decreases at higher elevations due to increased distance from the Earth's center, while also noting that buoyancy effects from the atmosphere are reduced.
  • A different viewpoint suggests that the effects of reduced gravity and decreased buoyancy may cancel each other out, leading to negligible changes in weight.
  • One participant provides a calculation indicating that the gravitational effect on weight loss at altitude is significantly greater than the buoyancy effect, supporting the idea that weight decreases with elevation.
  • There is a request for clarification on buoyancy equations and definitions of weight, highlighting potential differences in understanding among participants.
  • Another participant emphasizes that weight is typically defined as mass times gravity, suggesting that buoyant forces should not be included in this definition, although they acknowledge practical implications in measurements.
  • Concerns are raised about distinguishing between buoyant forces and other forces acting on the body, such as during movement or jumping.

Areas of Agreement / Disagreement

Participants express differing views on the definition of weight and the effects of buoyancy and gravity at higher elevations. There is no consensus on whether weight increases or decreases with altitude, and the discussion remains unresolved.

Contextual Notes

Participants highlight the complexity of defining weight and the influence of buoyancy, indicating that assumptions about definitions and measurements may vary. The discussion also touches on the difficulty of measuring these effects accurately.

Peter Pan
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My question is this…

As you move higher on Earth do you weigh more? I thought of this floating in a pool. The pressure around by body caused by the water allowed me to float? Air pressure is high at low altitudes and decreases as you go up.

So, do you weigh more standing on a mountain than at sea level?

Thank you
Pan
 
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Just the opposite, you weigh less at higher elevations. You are further from the Earth's center thus the laws of gravity come into effect. Any bouyancy effect due to the atmosphere is also reduced due to the thinner atmosphere, your body maintains the same volumn but at higer elevation, due to the reduced density of the air you displace less air, thus once angain weigh a bit more then at the bottom of the atmosphere.

Both of these effects are so small that it is nearly impossible to measure them, unless you are in orbit.
 
so, gravity being less, causing you to weigh less and a lower air pressure causing you to weigh more cancel each other out
 
Air is about 1/1000 the density of the human body. So the buoyant force on a person is about 1/1000 their weight, or just a few ounces.

If you go to the altitude where a jet flies (10,000m), the air is half as dense, so you lose half the buoyant force, which means you gain 1/2000 of your weight.

The Earth's radius is 6400km, so the loss in weight due to gravity change at 10km alt. is 2*10/6400 (the 2 comes from the fact that r comes into the force formula as a square).

This is 1/320, or 6 times more than the weight gain from loss of buoyancy. So Integral is right: the dominant effect is the gravitation dependence on distance from Earth's centre.
 
Can you post the bouyancy equations that you are referring to? It may be just a difference in the defination of "weight" but I've always thought of weight as mass*gravity. The other bouyancy forces would just be external forces and not truly affect the "weight"
 
Yes there are differing definitions of weight and I was sloppy: I simply used Peter Pan's definition, which appears to be the net downward force (gravity minus buoyancy). To be more precise, let weight be defined as the gravitational part alone. Then

Net force = Weight - Buoyant force = m g - m_air g

where m_air is the mass of the air displaced by the body. And of course g varies with distance h above the earth:

g = MG/(r+h)^2

HTH
 
I know that the topic isn't the definition of weight, but I believe it is mass*gravity. By peter Pan's definition(not saying he didn't know the right deffinition), Buoyant forces are included in the measurement of weight. This is certaintly true in practical measures of weight like scales, but buoyant forces are not really completely defineable, since it is hard to distinguish between say movement caused by buoyancy and movement caused by a sudden gust of wind. For instance, what if you jumped? would your weight momentarily be negative for some time? Although this is not buoyant forces acting, how can you distinguish between the two?

Although peter pan's definition could be true when applied to somthing like "the force towards an astronomic object with atmosphere"

[edit]Doh! appears Krab already clarified this[/edit]
 
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