What determines the number of propeller blades a vehicle has? | AskScience Blog

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Wednesday, January 26, 2022

What determines the number of propeller blades a vehicle has?

What determines the number of propeller blades a vehicle has?


What determines the number of propeller blades a vehicle has?

Posted: 26 Jan 2022 03:23 AM PST

Some aircrafts have three, while some have seven balded props. Similarly helicopters and submarines also have different number of propellers.

submitted by /u/Steve1924
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If you've taken an annual influenza vaccine for say 10 years, does that give a better protection for influenza in general even if you were to not take it a year and get influenza?

Posted: 25 Jan 2022 09:19 AM PST

Has there been any study done to prove if it offers milder symptoms? In my mind that would possibly give a broad T-cell protection for most new influenza mutations.

E: I came back to far more replies than I expected! Thanks everyone, I highly appreciate the many interesting answers.

submitted by /u/rosts
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How many watts are spend to raise the body temperature in case of a fever?

Posted: 26 Jan 2022 02:22 AM PST

How many watts does the body (M / 80kg or 176 lbs) use to raise the body temperature from normal (37° C or 98.5 F) to 40° C or 104 F during a fever? How many extra watts are spent to keep this higher temperature for an hour compared to normal body temperature?

And yes, you guessed it right. Currently, I'm sick AF and bored AF.

submitted by /u/rbienz
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With the Covid-19 vaccines nearing 10 billion administered doses, would that make it the most administered approved drug/treatment/preventative in history?

Posted: 26 Jan 2022 10:09 AM PST

I don't know what a blanket term for administered "medications" would be called when considering preventatives and treatments, but I'm also curious if the vaccine also beats out those things as well?

(So not just compared to other vaccines, but to other treatments for other diseases, including long term administrations)

submitted by /u/MCPE_Master_Builder
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Do electron holes actually "move" in a P-type semiconductor?

Posted: 26 Jan 2022 09:44 AM PST

All the explanations I read say a hole carries the charges by moving through the semiconductor. But how can a hole or void actually move? From my understanding the hole gets filled with an electron, which creates a new hole where that electron was, and another electron fills the new hole, and the cycle continues. So how is the hole itself moving? To me it seems more logical that it's a chain of filling holes rather than a void moving through matter.

*Also I'm sorry I'm not sure whether this questions is physics, chemistry, engineering, or mathematics so I just went chemistry

submitted by /u/Mydogatemyexcuse
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What determines how far fast moving gas can move through a gas?

Posted: 26 Jan 2022 03:31 AM PST

If I use my mouth/lungs to blow air with some speed, I can feel that gust of air a meter away, but not ten meters away. Are there some formulas for how far a fast moving gas can retain speed, or how much it slows down, moving in a gas like air? It would probably depend on several factors, including the initial speed and pressure of the surrounding gas.

A concrete example: is there a speed v such that if we accelerated CO2 to that speed, aimed upwards, it would make it out into space with enough speed to permanently leave the planet? Or would Earth's atmosphere slow it down to capture it again, regardless of the initial speed?

submitted by /u/Dagusiu
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Ask Anything Wednesday - Economics, Political Science, Linguistics, Anthropology

Posted: 26 Jan 2022 07:00 AM PST

Welcome to our weekly feature, Ask Anything Wednesday - this week we are focusing on Economics, Political Science, Linguistics, Anthropology

Do you have a question within these topics you weren't sure was worth submitting? Is something a bit too speculative for a typical /r/AskScience post? No question is too big or small for AAW. In this thread you can ask any science-related question! Things like: "What would happen if...", "How will the future...", "If all the rules for 'X' were different...", "Why does my...".

Asking Questions:

Please post your question as a top-level response to this, and our team of panellists will be here to answer and discuss your questions. The other topic areas will appear in future Ask Anything Wednesdays, so if you have other questions not covered by this weeks theme please either hold on to it until those topics come around, or go and post over in our sister subreddit /r/AskScienceDiscussion , where every day is Ask Anything Wednesday! Off-theme questions in this post will be removed to try and keep the thread a manageable size for both our readers and panellists.

Answering Questions:

Please only answer a posted question if you are an expert in the field. The full guidelines for posting responses in AskScience can be found here. In short, this is a moderated subreddit, and responses which do not meet our quality guidelines will be removed. Remember, peer reviewed sources are always appreciated, and anecdotes are absolutely not appropriate. In general if your answer begins with 'I think', or 'I've heard', then it's not suitable for /r/AskScience.

If you would like to become a member of the AskScience panel, please refer to the information provided here.

Past AskAnythingWednesday posts can be found here. Ask away!

submitted by /u/AutoModerator
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Can the Hubble telescope take a picture of the Webb telescope?

Posted: 25 Jan 2022 07:20 PM PST

Do their relative positions let them see each other?

submitted by /u/rajost
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What makes a liquide "swim able" ? (Viscosity? Density?)

Posted: 26 Jan 2022 02:39 AM PST

I'm thinking if there are liquids that no matter how hard you swim, you would simply sink.

submitted by /u/0K4M1
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If someone is infected with SARS-COV-2 before vs. after vs. no mRNA vaccination, would their non-spike (nucleocapsid/membrane/envelope) antibody reponses be similar, or different? Would they have similar levels of said antibodies? Would those persist for a similar length of time?

Posted: 24 Jan 2022 09:18 PM PST

In other words, if one person was infected before getting vaccinated, another was infected after getting vaccinated, and another was infected and never got vaccinated, would they have similar levels of non-spike antibodies, say, 6-12 months later? Or would the levels be higher/lower in one or the other?

I know it varies from person to person based on many different factors, so for the sake of argument, let's say these three people are biologically identical clones and they were all asymptomatic.

submitted by /u/Any_Camel628
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Would A Binary System Of A Star (Preferable a yellow dwarf) And An Equally Sized Black Hole Be Stable?

Posted: 26 Jan 2022 12:02 AM PST

(This is for a sci-fi project of mine). What stars would be best for this binary system? Would it be habitable? Would it be possible to place the planet in between the two celestial bodies? Thanks in advance!

submitted by /u/FoulPeasant
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Can someone explain lateralization vs localization in the context of focal and secondary genralized seizures?

Posted: 26 Jan 2022 03:46 AM PST

I hear the terms thrown around alot on my neuro placement (med student), but googling things hasnt helped much.

From what I understand, localization is where the focal part of the seizure displays signs typical of a certain part of the brain? For example something involving right motor cortex might cause head / gaze / arm movement towards the left side?

It's lateralization that confuses me. How is this different?

submitted by /u/97anon
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Where do the positrons come from that are used in PET scanners?

Posted: 25 Jan 2022 11:02 PM PST

I've read a few articles that state the antimatter is pretty rare in the universe. If I understand correctly, positrons are antimatter. Yet PET scanners are run for many hours each day in hospitals around the world, so it seems like they can't be too rare. If antimatter is so rare, where do the scanners get the positrons they use? Can PET scanners run out of positrons like a car runs out of gas?

submitted by /u/propertyq
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Why was Asia mostly ice-free during the last glacial maximum while Europe and North America were half-covered by glaciers?

Posted: 24 Jan 2022 08:19 PM PST

Permanent Magnets and "Finite Energy"?

Posted: 26 Jan 2022 07:58 AM PST

How can permanent magnets wich are said to lose 1-5% efficiency in 100 years not be a life time energy suply ? In other words: If they lose 1-5% of they'r energy every few good years why we dont use them for free electricity? Or we already do and it hided ?

I whould apreciate to get an answear to any of this 2 questions and whit all the "bs" that whould explain why magnets can't make an nearly endless suply of energy if the answear is no.

submitted by /u/Aggressive_Duty4997
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If someone is doing research on Schedule I controlled drugs, where do they get the drugs?

Posted: 26 Jan 2022 07:32 AM PST

Are they made in their own labs or does the government dole them out from drug busts/seizures after testing them thoroughly? Other ways of getting them?

submitted by /u/OKrakenmyKraken
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What determines if a substance is stringy?

Posted: 25 Jan 2022 12:18 PM PST

For example, why are mixtures such as xanthan gum + PVA glue + laundry detergent or acetone + polystyrene stringy? These materials aren't stringy on their own but when mixed they are. How could i make my own super stringy substance?

to clarify, by stringy i mean if you were to put your finger in there and pull it out, it would latch on and make a long rope

submitted by /u/Saltyboi24
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Does the size of a pan affect the time it takes for its center (the area directly above the stove fire), to heat up?

Posted: 26 Jan 2022 02:17 AM PST

To elaborate, lets say we have two pans with the same thickness and same material. The only difference being, one pan has a larger diameter. My question if I apply the same amount of heat to both pans, will the center of the smaller pan heat up faster than the center of the larger pan?

submitted by /u/entelal
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The mite genus, Adactylidium, has an unusual lifecycle, where males impregnate sisters while both are still inside their pregnant mother. How does this not cause the sort of genetic catastrophe that inbreeding is known for?

Posted: 24 Jan 2022 05:41 PM PST

From Wikipedia (in case I summarized any of it incorrectly): The pregnant female mite feeds upon a single egg of a thrips, growing five to eight female offspring and one male in her body. The single male mite mates with all the daughters when they are still in the mother. The females, now impregnated, eat their way out of their mother's body so that they can emerge to find new thrips eggs

submitted by /u/anarcho-onychophora
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Why urine is hypertonic to blood in normal physiological conditions?

Posted: 25 Jan 2022 08:06 PM PST

Would appreciate if someone can explain!

submitted by /u/Feeling_Position_129
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How do cracks propagate at a molecular level? Once a crack starts, what makes it stop?

Posted: 25 Jan 2022 08:41 AM PST

I'm currently looking into relationships between hardness, tensile strength, and ductility of a substance. What I mostly trying to focus on are brittle materials and the way that they practically completely shatter once a fracture begins. I'm looking for information that relates the initial force applied to how far a crack would propagate through an object. How much energy is lost as a fracture expands through an object? Is the amount of energy lost so small it's almost negligible in brittle objects?

I'm still looking for the answer to these questions, but for some reason I just can't find them. I might not be searching the right things apparently.

submitted by /u/KaptainTZ
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Can multiple objects orbit at L2 or has Webb effectively 'taken' it?

Posted: 25 Jan 2022 09:03 AM PST

How do we know for sure that red-shift in distant galaxies / stars is because they are moving away and not because of some other unknown effect on light traveling for insanely long times / distances?

Posted: 25 Jan 2022 08:39 AM PST

I know that there is probably something very basic that I am missing but this question keeps coming back into my head after years of thinking about it, and I can't find anything online that explains it (from a google search anyway).

I understand how the doppler effect works, and have no doubt that stars moving away WOULD be red shifted. But doesn't the fact that the farther away we look the more red shifted a light source is imply that there could be some effect on light that is due to the distance / time that light travels?

As an analogy the farther I look in earth's atmosphere, the less color saturated the objects appear to be - that's not due to anything about the objects themselves, it's because of the journey the light has to travel to get to me and the effects of the atmosphere. The fact there is such a clear correlation between color saturation and distance would lead me to believe that the effect is because of the distance itself, not due to some other effect which causes objects that are further away to be less color saturated. I'm not saying that's a possible explanation for the effect, just an analogy of the way you would interpret the data and whether the effect is due to some property of the source itself or a property of the journey the information takes to get to you.

Basically how have astrophysicists ruled out this possibility?

submitted by /u/3xpansion
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What causes the covid headache?

Posted: 25 Jan 2022 07:27 AM PST

Headache seems to be one of the most common symptoms of COVID-19. What actually causes it? Dehydration? Blood flow changes? Inflammation? Inquiring minds want to know!

submitted by /u/eldoctordave
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