Clear my concept of weightlessness

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    Concept Weightlessness
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Discussion Overview

The discussion revolves around the concept of weightlessness, particularly in the context of objects in orbit and free fall. Participants explore the definitions, implications, and nuances of weightlessness from both Newtonian and relativistic perspectives.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants assert that weightlessness occurs when the net force acting on a body is zero, using the example of a person in orbit where centripetal force balances centrifugal force.
  • Others challenge this view by questioning whether a person in orbit can truly be considered weightless, noting that while the apparent weight is zero, there is still a net force acting on the person.
  • A participant suggests that weightlessness is a state of mind, emphasizing that gravitational attraction still exists even if one is unaware of it while in orbit.
  • Another participant points out the distinction between inertial frames in Newtonian physics and General Relativity, suggesting that definitions of weightlessness may vary between these frameworks.
  • Some participants highlight the importance of understanding the definition of weightlessness, referencing external sources for clarification.

Areas of Agreement / Disagreement

Participants express differing views on the definition and implications of weightlessness, with no consensus reached on the correct interpretation or the role of forces in this context.

Contextual Notes

There are unresolved issues regarding the definitions of forces in different frames of reference, as well as the implications of circular motion and gravitational effects on weightlessness.

hacker804
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Need to ask a question.
Weightlessness occurs when the net force acting on a body is zero.For example,consider a person in orbit.The centripetal force provided by gravity of the Earth is balanced by the outward centrifugal force therefore the net force on the person becomes zero and he becomes weightless.

^^Am I right?

Thanks.
 
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hacker804 said:
Weightlessness occurs when the net force acting on a body is zero.
Imagine yourself standing on the ground. The net force on you is zero. Are you "weightless"?

For example,consider a person in orbit.The centripetal force provided by gravity of the Earth is balanced by the outward centrifugal force therefore the net force on the person becomes zero and he becomes weightless.
What we call "weightlessness" occurs when the support force on a object is removed, such as when you are in free fall. Or in orbit.

"Centrifugal force" is an inertial force that appears when analyzing things from an accelerated, non-inertial frame of reference (a rotating frame of reference). I recommend that you stick to an inertial frame. There is a net force on a person in orbit, but his apparent weight is zero since the ship exerts no support force on him.
 
"weightlessness", in orbit (or in free fall) is just a state of mind. You are attracted to the Earth just the same as if you were standing on a tall tower at the same altitude. However, you are blissfully un-aware of this because everything that's going round ( the ship) with you is accelerating at the same rate.

This is a simplification because the different parts of the ship and you are at different distances from the centre of Earth and because they are all orbiting at the same rate, there is a detectable amount of 'microgravity' between objects around you at different distances.
 
hacker804 said:
Need to ask a question.
Weightlessness occurs when the net force acting on a body is zero.For example,consider a person in orbit.The centripetal force provided by gravity of the Earth is balanced by the outward centrifugal force therefore the net force on the person becomes zero and he becomes weightless.

^^Am I right?

Thanks.
If you consider a person in orbit to be in circular motion then the resultant (NET?) force is not zero. Circular motion requires a resultant force (for an object in orbit this is normally taken to be the centripetal force, Centrifugal force is not a real force !) you will get lots of responses to this...good luck in sorting them out.
 
The confusion comes the fact that an inertial frame of reference in Newtonian physics is not the same as an inertial frame in General Relativity. In GR, the statement "Weightlessness occurs when the net force acting on a body is zero" is reasonable, I think.
 

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