Clear my concept of weightlessness

In summary: ,in summary, weightlessness occurs when the net force acting on a body is zero. in orbit or in free fall.
  • #1
hacker804
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0
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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  • #2
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.
 
  • #3
"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.
 
  • #4
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.
 
  • #5
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.
 
  • #6

1. What is weightlessness?

Weightlessness, also known as zero gravity, is the state in which an object or person experiences a lack of apparent weight due to the effects of gravity being countered by other forces. This can occur in space or during freefall, where the object or person is in a constant state of falling towards Earth without actually making contact with a surface.

2. How does weightlessness affect the human body?

Extended periods of weightlessness can have various effects on the human body, such as muscle and bone loss, changes in blood flow and pressure, and alterations in the vestibular system (which controls balance and spatial orientation). These effects can be mitigated through exercise and other countermeasures, but they can still have long-term consequences for astronauts.

3. What causes weightlessness?

Weightlessness is caused by the balance of forces acting on an object or person. In space, the force of gravity is countered by the centrifugal force of the object's orbit around a larger body (such as the Earth). During freefall, the force of gravity is countered by the aerodynamic drag of the falling object. In both cases, the result is a state of apparent weightlessness.

4. Is weightlessness the same as being in a vacuum?

No, weightlessness and being in a vacuum are two different concepts. Weightlessness refers to the apparent lack of weight caused by the balance of forces, while a vacuum is a space devoid of matter and air pressure. Objects can experience weightlessness in a vacuum, but they can also experience it in other environments such as during freefall or in a spacecraft.

5. How is weightlessness simulated on Earth?

Weightlessness can be simulated on Earth through various methods such as parabolic flights, where an aircraft follows a curved flight path to create short periods of freefall, or through neutral buoyancy in a large pool of water. These simulations allow astronauts to experience weightlessness and train for space missions before actually going into space.

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