What is Weightlessness: Definition and 35 Discussions

Weightlessness is the complete or near-complete absence of the sensation of weight. This is also termed zero-G, although the more correct term is "zero G-force". It occurs in the absence of any contact forces upon objects including the human body.
Weight is a measurement of the force on an object at rest in a relatively strong gravitational field (such as on the surface of the Earth). These weight-sensations originate from contact with supporting floors, seats, beds, scales, and the like. A sensation of weight is also produced, even when the gravitational field is zero, when contact forces act upon and overcome a body's inertia by mechanical, non-gravitational forces- such as in a centrifuge, a rotating space station, or within an accelerating vehicle.
When the gravitational field is non-uniform, a body in free fall experiences tidal effects and is not stress-free. Near a black hole, such tidal effects can be very strong. In the case of the Earth, the effects are minor, especially on objects of relatively small dimensions (such as the human body or a spacecraft) and the overall sensation of weightlessness in these cases is preserved. This condition is known as microgravity, and it prevails in orbiting spacecraft.

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  1. shk

    What is the condition of true weightlessness?

    I think only happens when gravity is zero. But as gravity of Earth won't be zero , we need to be somewhere between Earth and Moon so the g of moon and Earth cancel each other out . At this point we will have true weightlessness. Is this correct and enough?
  2. Nantes

    Vacuum cleaner in a weightless environment

    Sorry for the vague title, I really wish the title character limit was longer. Suppose you are floating in space without gravity, but instead of a vacuum, there is air all around you. You turn on a powerful vacuum cleaner with the nozzle pointed directly ahead of you. Ignore torque/rotational...
  3. Vengo

    Why are astronauts outside a spaceship not pulled by Earth's gravity?

    Another Doubt Guys, I was watching this video on youtube. it is about weightlessness in space. it states that the astronauts inside a spaceship fly in space not due to zero gravity but due to centripetal force with which the satellite is revolving the earth. My question is "then why the...
  4. B

    Calculating time of zero g (Glider)

    Homework Statement [/B] Finding equation allowing to calculate time of zero-g (weightlessness) in a parabolic flight using non-powered glider (no thrust). Homework Equations [/B] I have found a few ways to calculate the time (here is one example which is basing on aircraft's velocity only -...
  5. 1

    Why is there "weightlessness" on the top of a verticle circle?

    i'm ashamed, that i never understand this, eventhough I'm studying quantum mechanics... so... why is there "weightlessness" on the top of a verticle circular motion? ie, if a plane if flying in verticle circles, why is there weightlessness while on the top of a circular path? i mean, if it's...
  6. chi_rho

    Travelling to Mars at constant velocity? Weightless?

    If I'm traveling on a spaceship at a constant velocity (say 10000 m/s) towards Mars will I feel weightless, or will I feel nearly weightless because I will still be slightly affected by gravity? I know that when astronauts are in the ISS they feel weightless because they are in a constant...
  7. S

    Weightlessness in Free Fall: What's Going On?

    Normally in a free fall , there will be gravity acting to your body but when we free fall , we don't really feel the force , we feel weightless ( ignoring air resistance ) , ( not in contact with anything). Why?
  8. T

    Does High Jumping Cause Weightlessness?

    Why a man clearing a bar in a high jump experiences weightlessness?
  9. S

    Satellite in Space: Why Freely Falling?

    Q1 Why does a satellite(or any space capsule etc) moving in a stable circular orbit around Earth behaves like a freely falling body?? Q2 Why do the astronauts in these capsules are said to be in weightless condition?? i m not much convinced with the solutions to my doubts so i would appreciate...
  10. T

    Apparent weightlessness problem?

    Homework Statement A roller coaster goes over the top of a semicircular track of radius R with a velocity Vtop, such that passengers momentarily feel weightless (zero 'g') at the top. The rollercoaster then accelerates to the bottom of another semicircular track of the same radius R. What...
  11. Q

    Simple question about zero gravity and weightlessness

    Ok, I have to do my case study on zero gravity but I am just not understanding it. It says weightlessness is similar to when you are in a free fall, for example in an elevator because you are accelerating at gravity's force? I don't get what EXACTLY makes us weightless just because we are free...
  12. chaszz

    What causes weightlessness in a free fall?

    Einstein said one his happiest realizations was that a person in free fall would feel no weight. Unless I am mistaken he said this. But didn't Newton realize this?
  13. H

    Clear my concept of weightlessness

    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...
  14. A

    Why Does a Shuttle Need to Be in a Circular Orbit for Apparent Weightlessness?

    Is it important that a shuttle surrounds the Earth in an circular orbit in order the astronauts (and the shuttle itself) to have 0 apparent weight and so be considered as in state of apparent weightlessness?
  15. S

    Weightlessness in a common swing

    Hi, Our sensation of weight is given by gravity together with normal forces. It is said that in a swing you'll feel weightless at the top of the ride (180 degrees), because there is no seat that gives you normal force. But from my experience there is something strange even before 180 degrees...
  16. D

    Exploring Weightlessness on a Frictionless Roller Coaster

    Homework Statement Consider a frictionless roller coaster such as depicted below. The acceleration of gravity is 9.8 m/s2. Passenger cars start at point A with zero initial speed, accelerate as they go down to point B, swing around the circular vertical loop B ! C ! B of radius 30 m...
  17. N

    A question about conditions for Weightlessness

    I read that if you are in a spaceship orbiting Earth in a circular motion, the astronout feels weightless (meaning the normal force to the astronout is equal to zero). But according to Newton laws equations you get: and then if we assume N=0 (which is really what's happening according to my...
  18. R

    Is weightlessness in orbit just a result of horizontal velocity?

    To explain weightlessness to my students, I use the analogy of a falling elevator (lift) as folows - if we stand on weighing scales in an elevator and the elevator cable snaps, the scales will show zero since they are falling to the ground at the same acceleration as us, therefore registering no...
  19. S

    Circular Orbits and weightlessness

    Homework Statement A small projectile is launched parallel to the ground at height h = 1 m with sufficient speed to orbit a completely smooth, airless planet. A bug rides in a small hole inside the projectile. Is the bug weightless? Explain. The Attempt at a Solution I didnt understand...
  20. S

    Creating Weightlessness in an Airplane: Calculating Flight Path Radius

    Homework Statement An airplane in a wide "outside" loop can create an apparent zero eight inside the aircraft cabin. What must be the radius of curvature of the flight path for an aircraft moving at 749 km/h to create a condition of weightlessness inside the aircraft? Assume the acceleration...
  21. T

    Weightlessness physics question

    Okay the problem statement is in a word document because I had to include a diagram. Please check it out. okay to experiece weightlessness, I know that acceleration due to gravity has to equal gravitational field strength. What bothers me is how do you experience weightlessness when there...
  22. R

    Weightlessness discoveries in the history of the human race

    What are the major weightlessness discoveries in the history of the human race and how will they be of benifit to our future?
  23. S

    Weightlessness on a Ferris Wheel

    Homework Statement How many revolutions per minute would a 15.1 m diameter Ferris wheel need to make for the passengers to feel "weightless" at the topmost point of the trip? Homework Equations The Attempt at a Solution I assume this problem has something to do with finding...
  24. S

    Weightlessness due to gravitational field

    Astronauts in a space capsule orbiting the Earth at a height of 900km experience weightlessness: hence the gravitational field due to the Earth must be zero at that altitude'. Can someone please help ? What does it mean?
  25. B

    What Distance from Earth Achieves Weightlessness for Astronauts?

    Homework Statement How far away from Earth does a spacecraft have to be for the astonauts in it to be weightless? Homework Equations The Attempt at a Solution Is this correct: Since the gravitational force is a long range force, no matter what finite distance the...
  26. B

    Weightlessness; Ferris Wheel

    Homework Statement The apparent weight a person feels is the normal force that acts on the person. Suppose a Ferris Wheel has a diameter of 28.om and makes one revolution every 13.3 seconds. What is the ratio of a person's apparent weight to real weight a) at the top and b) at the bottom...
  27. B

    Why do astronauts feel weightless in space?

    The astronaut in space feels weightless, yet he has weight. Could you guys explain? I have an idea but not quite sure...
  28. A

    Weightlessness while in the air

    when i jump, while I'm in the air ( no air friction), my weight would be zero, right? but the equation W=mg doesn't consider that. g and m would be constant so my weight would be the same.:frown: am i missing something?
  29. R

    Sensation of weightlessness homework

    The sensation of weightlessness in a spacecraft in orbit is due to: a) abscense of gravity b)acceleration in orbit equal to acceleration due to gravity. c)Shielding from gravity provided by spacecraft d) spacecraft in orbit has no energy I would mark a) right. do you agree?
  30. M

    Jumping, weightlessness and movement in tennis

    I have just jumped up in air and when my feet hit the ground my body is weightless for a couple of seconds isn't it? Is this why when in tennis that when you do a split step that you can move so fast in ether direction because you are weightless when your feet touch the ground?
  31. P

    Why do astronauts feel weightless in orbit?

    Why does an astronaut in a spacecraft orbiting the Earth experience a feeling of weightlessness?
  32. J

    Weightlessness and sound waves

    What are the effects of weightlessness on sound waves, if any? [Not talking about human hearing or ability to locate sound]
  33. S

    Weightlessness on Earth's Surface

    Suppose that I am standing on the surface of the Earth. Then the only forces acting on me is the force of gravity that is pulling me down and the normal force exerted by the ground that is pushing me up. These forces are equal and opposite in direction and thus there is no net force acting on...
  34. H

    Weightlessness in the Center of The Earth?

    Is it true that if you dig a tunnel to the center of the Earth you will experience weightlessness? I heard that you will get heavier then become weightless.
  35. T

    How Long Would a Day Be If the Earth Rotated Fast Enough for Equatorial Objects to Be Weightless?

    Hi everyone I am a student in a mechanics course. We just had a brief intro into gravitation and Newtons synthesis and I was wondering how I can solve this question... How long would a day be if the Earth were rotating so fast that objects at the Equator were weightless? The reading on...