What caused the growing whining sound when old propeller planes went into a nose dive? |
- What caused the growing whining sound when old propeller planes went into a nose dive?
- How does heat transfer between a solid to a liquid?
- Has global warming had any noticeable changes in animal migration patterns?
- Is it ever possible to move at a negative speed?
- Is a Mach 3 sonic boom louder than a Mach 1.5 sonic boom? Would travelling super sonic for longer periods of time increase the loudness or intensity of the boom?
- Experimental fusion rectors on earth require temperatures hotter than the sun. Since the sun has the process of fusion at 15million degrees, why do we need higher temperatures than the sun to achieve it?
- How does turning on AC with heat actually help to defog a car windshield?
- How does a plant know which way is up so that it can grow in that direction?
- What is laminar flow?
- On a molecular level, what differentiates spring steel from regular steel?
- Why does the boiling point of water rise when you put salt in it?
- What is the difference between a external and internal force?
- Can you explain me the electroweak interaction in a simple way?
- Why do insulators have a large band gap?
- What methods are there for solving the quantum many-body problem?
- If anything having mass has an equivalent amount of energy and vice versa, does heating up an object change its mass? How?
- If light, travelling from denser to rarer medium, is incident at an angle equal to the critical angle, it grazes the surface. However, a light traveling along the surface will not enter the medium from that same point. Is it a violation of the principle of reversibility?
- How does a turbojet reduce the intake's air velocity to subsonic speeds when aircraft it's powering is traveling at super sonic speeds?
- How are there only 7 orbitals for the “f” shape of electrons?
| What caused the growing whining sound when old propeller planes went into a nose dive? Posted: 05 Jan 2019 08:31 AM PST I'm assuming it has to do with friction somewhere, as the whine gets higher pitched as the plane picks up speed, but I'm not sure where. Edit: Wow, the replies on here are really fantastic, thank you guys! TIL: the iconic "dive-bomber diving" sound we all know is actually the sound of a WWII German Ju87 Stuka Dive Bomber. It was the sound of a siren placed on the plane's gear legs and was meant to instil fear and hopefully make the enemy scatter instead of shooting back. Here's some archive footage - thank you u/BooleanRadley for the link and info Turns out we associate the sound with any old-school dive-bombers because of Hollywood. This kind of makes me think of how we associate the sound of Red Tailed Hawks screeching and calling with the sound of Bald Eagles (they actually sound like this) thanks to Hollywood. Thank you u/Ringosis, u/KiwiDaNinja, u/BooleanRadley, u/harlottesometimes and everyone else for the great responses! Edit 2: Also check out u/harlottesometimes and u/unevensteam's replies for more info! Edit 3: The same idea was also used for bombs. Thank you u/Oznog99 for the link! [link] [comments]  |
| How does heat transfer between a solid to a liquid? Posted: 06 Jan 2019 06:39 AM PST So, I understand the process is called convection (right?), and I understand how convection works, but I'm curious about what is happening on the molecular level. If I understand it correctly, the molecules of a substance move (or vibrate or something like that) at different speeds depending on their relative heat. Hotter things move/vibrate faster, cooler things move/vibrate slower, and solids are so cold that their molecules are hardly moving at all, so the entire substance is locked up in the form of a solid. I know this is super simplified and probably full of over generalizations, but I just want to lay down the concept first. Now we come to the root of my question: Lets imagine a glass of cold water, sitting on the table. For the sake of my poor analogy, lets forget about the part where the air touches the water (say the glass has a lid on or something). Now, the water will gradually increase to room temperature through convection. Here's the bit I don't understand. On the molecular level, the glass will have to heat up first. The heat in the air will warm the glass, which will warm the water in the glass. But the glass is a solid, and will remain so at very high temperatures. So its molecules would be moving very slowly, right? Slower than the molecules of the liquid water, right? But the glass is warmer than the water, because it has a higher melting point, and therefor transfers heat to the water. So how do slower moving/vibrating molecules transfer their greater heat/energy to faster moving/vibrating molecules? If this belongs on a different subreddit, please let me know. [link] [comments]  |
| Has global warming had any noticeable changes in animal migration patterns? Posted: 05 Jan 2019 03:37 PM PST |
| Is it ever possible to move at a negative speed? Posted: 06 Jan 2019 05:56 AM PST Would this always be classed as some form of 'reversing' or would moving back in time be classed as a negative speed? Or is there simply no such thing and it's always a positive speed? [link] [comments]  |
| Posted: 05 Jan 2019 10:44 AM PST If I understand correctly - The waves essentially cannot get out of the way quick enough when travelling supersonic and they get all bunched up. So, i have been curious to find out if speed and duration have an effect on the intensity of the sonic boom. [link] [comments]  |
| Posted: 05 Jan 2019 04:45 PM PST |
| How does turning on AC with heat actually help to defog a car windshield? Posted: 05 Jan 2019 05:11 PM PST From reading various tricks to help defog the car window, people recommend turning on the AC with high heat. However if it's set to heat the car, doesn't it bypass the AC condenser and just pump hot air from the radiator without the benefit of condensation on the condenser coils? [link] [comments]  |
| How does a plant know which way is up so that it can grow in that direction? Posted: 05 Jan 2019 09:11 PM PST |
| Posted: 05 Jan 2019 08:53 PM PST Have u guys seen some pictures/videos of a seemingly steady stream of water flowing downwards, but when a guy touches it, it behaves like a normal water stream. How does that work? Link: https://www.reddit.com/r/blackmagicfuckery/comments/acvvwy/laminar_flow/?st=JQKZPWRL&sh=04837908 [link] [comments]  |
| On a molecular level, what differentiates spring steel from regular steel? Posted: 05 Jan 2019 08:49 PM PST |
| Why does the boiling point of water rise when you put salt in it? Posted: 05 Jan 2019 09:57 AM PST I understand that when you impurities in to a liquid like water that the boiling point would rise, but when you put salt into water, it dissolves and free ions roam through the water. Because of the free ions electricity can be conducted throughout the water. Shouldn't it be the case that because of the free movement of electrons, heat also conducts more easily in the liquid and as a result the boiling point would decrease? [link] [comments]  |
| What is the difference between a external and internal force? Posted: 05 Jan 2019 08:28 PM PST Why is compression a internal force? Can't it be a external force because gravity continuously compresses oneself? [link] [comments]  |
| Can you explain me the electroweak interaction in a simple way? Posted: 05 Jan 2019 09:52 AM PST Can one of you guys please explain me how does the electroweak interaction work and in which way do electromagnetic and weak force interact? [link] [comments]  |
| Why do insulators have a large band gap? Posted: 05 Jan 2019 06:45 PM PST So I understand that insulators and conductors have a large bandgap, so you need to excite the electrons to move them to the conduction band to allow electricity to conduct, and I also understand that for metals, the valence and the conduction bands are continuous so that electrons can just go to the conduction band when positive and negative ends are established, but why is it that insulators have such a large band gap in the first place, whereas metals do not? Appreciate any help! [link] [comments]  |
| What methods are there for solving the quantum many-body problem? Posted: 05 Jan 2019 08:57 AM PST |
| Posted: 05 Jan 2019 09:55 AM PST The mass-energy equivalence states that anything having mass has an equivalent amount of energy and vice versa. If we have a mass of metal and we heat it by some x decrees Celsius then it's potential (correct definition?) energy increases. This is what I recall from my Physics classes. But how does heating up an object increase that object's mass? How does it lose mass as it cools? [link] [comments]  |
| Posted: 05 Jan 2019 08:28 AM PST |
| Posted: 05 Jan 2019 10:03 AM PST I'm trying to get a better understanding of turbojets, and one thing I've seen mentioned is that the air speed inside the engine has to be below the speed of sound. Why does the intake air speed have to be subsonic and how is it slowed? Does a ramjet accomplish slowing the air using the same principal? And what allows a scramjet to work with the intake air being super sonic? [link] [comments]  |
| How are there only 7 orbitals for the “f” shape of electrons? Posted: 05 Jan 2019 10:23 AM PST When subdividing the periodic table into sections for the orbital shapes s, p, d, and f, you can see that there are 15 elements horizontally in the "f section". However every shape must have two electrons in each orbital, but 15 is not evenly divisible by two (and to my knowledge you can't have a half-orbital). What is the cause of this, or how can it be explained? [link] [comments]  |
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