# Myuncle

Senior Members

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• Lepton

7

1. ## Astronauts weightlessness: free fall or centrifugal force?

ah ok, I will read more about the vomit comet, maybe it's a good way to understand the subject.
2. ## Astronauts weightlessness: free fall or centrifugal force?

You mean that if you are falling inside the elevator moving sideways, the orange will stay in front of you instead of touching the floor? An aircraft can move as fast as a free falling elevator, wouldn't be the same situation?
3. ## Astronauts weightlessness: free fall or centrifugal force?

We is me...or common mortals like me. Not everyone has your expertise swansont, relax. I am talking about the centrifugal force, because it is rarely mentioned as the cause of weightlessness in the ISS astronauts case. The case of free falling is when there is only gravity acting, but in the case of a satellite, shuttle or ISS, you need rockets to move that fast, that's why I would say that they are spinning, they are not free falling. Example, if you are dropped inside an elevator, you are free falling vertically (not spinning around the earth), at about 300 km/h, and the weightless sensation, in this case, is given by the free fall, your feet don't stay on the floor, and if you try to drop an orange, it won't go to the floor, but will float in front of you. Second example, you are inside an aircraft travelling at a constant 300 km/h, just like in the free falling elevator, but I guess you won't feel any weightlessness sensation, you stay seated, and if you try to drop an orange it will fall down on the floor. Third example, you are on a roller coaster, going up fast, at the top of the track, for a moment you will feel weightless, lifted out of the seat, the orange will stay afloat. Which of these example can be associated to the astronauts weightlessness? To me only the third example, for the ISS men it will feel like and endless "top of the roller coaster hill". Yes, the cannonball example is useful to understand why things can spin around the earth, but it doesn't make you understand the weightlessness sensation inside a ship.
4. ## Astronauts weightlessness: free fall or centrifugal force?

and that's what I don't understand, how can it be considered a freefall if it never go towards the centre of the earth?
5. ## Astronauts weightlessness: free fall or centrifugal force?

Our fastest aircrafts travel at about 800 km/h, which is nothing compared to the ISS (27.600 km/h). But if you could travel at that speed with an aircraft would you experience the same weightlessness?
6. ## Astronauts weightlessness: free fall or centrifugal force?

Sorry, double post, how can I delete it? Yes, in fact to me the ISS is not freefalling, as I read often. Don't you think the word freefall has nothing to do with the orbits cases of most satellites and ISS?
7. ## Astronauts weightlessness: free fall or centrifugal force?

When we see the astronauts clips in the ISS or the old Shuttle, we think that they are floating because there is no gravity. In factthe gravity in those orbits is almost the same as here on earth. So what keeps them floating is a never ending freefall. That's what I was reading, but I am having problem to understand it well. As I see it the ISS or the Shuttle, is not freefalling, but is just moving damn fast, so fast that it can escape the gravity pull. A freefall example to me would imply that you are falling towards the centre of the earth, and not east or west. When we are dropped from a tower, sitting on a chair, or inside an elevator, we would experience a weghtless sensation, the same as the astronauts, but this is indeed a freefall, because there is a downwards direction. In the case of the ISS, to me it's not a freefall, but the weightlessness is given by a constant balance between centrifugal force, speed of the ship, and gravity. What do you think?
8. ## How efficient can a solar panel be indoor?

Let's say that I power a solar panel indoor (underground or under roof) with artificial light, and I place a concave mirror on top of both the solar panel and the light, how efficient would this be?
9. ## A misunderstanding about multiplication

That's interesting. When we say 6m, we never specify 6m of what, is it 6m of tape? 6m of chalk? 6m of atoms? 6m of air? 6m of nothingness? If it's 6m of atoms, then it is not just 6m, because atoms have a thickness....
10. ## "Wind" turbines in a vacuum

If you end up with lowering the energy output, I can't argue with that. I was hoping it would be the opposite. I imagined turbines sealed in a vacuum, in a horizontal position, to lower the friction you could even put rollerblade wheels at the end of the blades. And also they could be placed underground. How much energy is required to spin them, if you can push them by hand, why not using a bit of electricity?
11. ## "Wind" turbines in a vacuum

Why they don't seal the turbines inside a vacuum? By watching this clip, https://www.youtube.com/watch?v=WTt_hoWtMIc, is clear that a wheel would spin much longer inside a vacuum. So, let's say that you use a normal wind turbine (or solar panels) to activate 10 other turbines sealed in a vacuum. It would be like multiplying the energy. What do you think?
12. ## What happens if you jump inside a vacuum chamber?

Yes that's a big chamber. It would be interesting to see how humans would move inside. Unfortunately there are no footages. The only clip I saw it is a spacesuit test in 1965, the spacesuit starts leaking, the man survives, but look at the way he falls at 1:43, he's almost floating, not too much, but I've never seen someone falling like that. Clip:
13. ## I don't understand Theory of Relativity: A)I am not clever B)Nothing to understand

As a measuring tool? We can't get away from using time and clocks. But take my answers always with a pinch of salt, I am not the expert here, I just try my luck when I write...
14. ## I don't understand Theory of Relativity: A)I am not clever B)Nothing to understand

Well, I don't need it, but for 1 million pounds I can use it
15. ## I don't understand Theory of Relativity: A)I am not clever B)Nothing to understand

Yes, but I agree with you on this. I just don't agree with confusing the verb need with the verb use.
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