Confusion spinning falling objects vs spinning objects

In summary, the Earth's gravity has less effect on astronauts in space, causing them to feel weightless. This is due to the Earth's gravitational attraction being only 11% less at the altitude of a spacecraft compared to the surface. The reason why astronauts feel weightless is because they are continuously falling towards the Earth, but never reaching it due to the Earth's curved surface. The weak gravitational force is also why we do not see the effects of gravity between objects in a spacecraft. In a thought experiment, an object in orbit would take the same amount of energy to spin as an object on Earth, as the difference in weight is not a factor in determining the energy needed.
  • #1
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OK, so this is what I read:

<< Moderator added link for attrubution >>

http://education.jlab.org/qa/gravity_01.html

In space we feel weightlessness because the Earth's gravity has less effect on us. Why do we not see the effect of the gravitational force between the various objects in a spacecraft ? We see them floating around. Since the objects in a spacecraft are comparatively close to each other we should be able to see the gravitational effect between them.

Although the Earth's gravity has a lesser effect on an astronaut orbiting the Earth in a spaceship than on a person on the surface of the Earth, this is not the reason why an astronaut experiences weightlessness. The space shuttle, International Space Station and most other manned vehicles don't get that far from the Earth. The Earth's gravitational attraction at those altitudes is only about 11% less than it is at the Earth's surface. If you had a ladder that could reach as high as the shuttle's orbit, your weight would be 11% less at the top. Put another way, a person who weighs 100 pounds on the Earth's surface would weigh about 89 pounds at the top of the ladder.

The reason why the person wouldn't feel weightless is because they are being pushed by the ladder - it is keeping them from falling. If they were to jump off the ladder, then they would feel weightless, at least up until the time they splatted on the ground. This is why astronauts feel weightless. The astronaut, the spaceship and everything inside it are falling towards the Earth. The reason why the astronaut doesn't go splat is because the Earth is curved and the astronaut, the spaceship and everything inside it are moving 'sideways' fast enough that, as they fall towards the Earth, the surface of the Earth curves away from them. They are always falling towards the Earth, but they never get there.

The reason why you don't see gravitational effects between objects in a spacecraft is because gravity is a very, very weak force. Of the four basic forces that scientists are sure about, gravity is, by far, the weakest one. Have you ever tripped and fallen down? Well, it took the whole planet to do that to you. Have you ever seen a sock stick to a shirt after it has come out of a dryer? That static cling, created by a slight imbalance of charge between the sock and the shirt, is stronger than the gravitational attraction of the Earth. The gravitational attraction between two small objects in a spacecraft would be overwhelmed by other forces, such as the force of the air being circulated throughout the spacecraft . Although the force of attraction is there, it is so weak that special care would have to be taken to notice it.

Here's what I'm confused about. Let's say there is an object that weighs a ton on Earth's surface and a replica of that object in orbit at the distance where it weighs 11% less. Let's say I want to get them both spinning at the same RPM just because. I'm guessing the object in orbit takes less energy to get spinning at the same RPM as the object on Earth but how much less? Will the fact the the object in orbit is "falling" cause it spin more easily than just 11% easier? Or is the amount of force to spin the object defined by its weight? I'm not really sure where to start but I want to find out the answer to this pretty bad.

And if someone knows all these answers... how much energy would it take to spin a third replica of the object on Earth, to the same RPM as the other two objects, so far from any gravitational pull that it is truly weightless?
 
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  • #2
The object in orbit will take the same amount of energy to spin at the same rpm.
What you are mixing is mass and weight. The weight is what a scale would show as the result of a measurement. In the thought experiment on orbit the scale woudl show 11% less than on the surface of the earth. But the inherent (gravitational) mass the object has stays the same. Now the energy need to send the object spinning depends on moment of inertia, which itself depends on (ineratial) mass. To current date no difference between ineratial and gravitational mass has been measured.

So to send the object spinning you will need the same amount of energy, no matter where the object is in the gravitational field. (Of course this only holds for reasonably sized obejcts)
 

What is the difference between confusion spinning falling objects and spinning objects?

Confusion spinning falling objects and spinning objects are two different types of motions that can occur in an object. Confusion spinning falling objects refer to the motion of an object that is both rotating and falling at the same time, while spinning objects refer to the motion of an object that is rotating around a fixed point.

How does confusion spinning falling objects occur?

Confusion spinning falling objects occur when an object is both rotating and falling at the same time. This can happen when an object is thrown or dropped from a height while also spinning, or when an object is rotating on a surface that is not fixed.

What is the cause of spinning objects?

Spinning objects occur when an object is rotating around a fixed point. This motion is caused by the object's angular momentum, which is the product of its mass, velocity, and distance from the axis of rotation.

What are some real-world examples of confusion spinning falling objects?

Some real-world examples of confusion spinning falling objects include a falling leaf that is also spinning, a spinning coin that is dropped from a height, or a frisbee that is thrown with a spin while also falling to the ground.

How do confusion spinning falling objects and spinning objects affect an object's stability?

Confusion spinning falling objects can often lead to an object being less stable, as the combination of rotating and falling can cause the object to become off-balance. On the other hand, spinning objects can help stabilize an object, as the angular momentum can counteract any external forces acting on the object.

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