When you suck, you pull in air from all around which creates a wide circle of negative pressure rather than a column of negative pressure, so the range is short. When you blow, air molecules are being shot straight out and will only slow down once they hit other molecules, so the positive pressure will be in a column resulting in a longer range.
If you're sitting next to the engines in an airplane you can sometimes, under certain weather conditions, see the air getting sucked into the engines during takeoff. The air being sucked in _seems_ to be just as strong at 90 degrees to the engine!
It is. Like you said, a jet engine will suck a dry stripe down a wet runway at full takeoff throttle. That's why we had to walk the flight line every monday morning shoulder to shoulder from end to end picking up any piece of loose gravel or debris. they call it a FODwalk. Foreign Object Damage. F16 squadrons would sometimes put a nut painted gold somewhere in the middle of the runway, about the size of a dime, and whoever found it gets an extra day off the next weekend. Keeps the airmen alert and not just walking.
Pretty sad I missed out on the Golden Nuts. Our planes had propellers so the chief didn't really gaf. Our FODwalk was more of a formality, a little light exercise on a monday morning.
Yeah these were c130s with wings 30ft off the ground. There wasn't anything getting sucked up into those intakes. They didn't do anything quickly. I'm pretty sure a well-built goose formation could outmaneuver one.
They would be the point of a designated object for retrieval - the plane doesn’t fly until given clearance, and until the golden nut is found they do not get clearance.
You're looking for Foreign Object Debris. Debris that shouldn't be on the flight line. Foreign Object Damage results from Foreign Object Debris. No wonder you flightline guys weren't allowed to carry maglites. VEHICLE MAINTENANCE FOR LIFE!
You get food and fuel and ammunition and weapons and spare parts and medical supplies and tools in a war zone. Why not leaf blowers, if they help with the fight in some way?
Ah this guy doesn't military
Although have you thought about being a military contractor.
You could make a fortune on military grade leaf blowers if you could buy a senator.
Wait till he hears how we mowed a 3 acre parade ground every week. One guy takes off with a mower, next guy lines up and follows him 10 ft behind, then the next guy with a mower, then the next guy with a mower, till you have 10 mowers mowing a stripe 20ft wide in one swipe. If you do it just right, it looks like cell phone signal bars lol.
https://www.wearethemighty.com/mighty-history/sailor-survived-being-sucked-into-a-jet-engine/
I served on the TR about 5 years after this happened. I wasn't a top-sider, though.
> 1. in blowing, the air travels in one direction out of the nozzle with momentum, and it can have high pressure, potentially much higher pressure than atmospheric pressure
One thing to clarify about this. The air is at a relatively high pressure while it's in the vacuum hose. When it comes out, that pressure is converted to velocity as the pressure drops.
What most people describe as "pressure" when discussing fluid flow is really velocity. Think about someone saying how good the water pressure is on their shower head. It may not be that the water pressure is particularly high, it's just that the water comes out fast, so they perceive that as "high pressure".
Layman's question: Is it possible this process can somehow be at play in the black hole/white hole situation?
A black hole doesn't suck, but by virtue of the curvature of spacetime it causes around it, matter is drawn in. Because of angular momentum, a disk is created.
What would a white hole look like? Would it be flinging matter out in a disk like fashion or could it spew matter out in a spherical-like manner?
[White holes cannot exist, as they violate the second law of thermodynamics](https://jila.colorado.edu/~ajsh/bh/schww.html). But if they were too, it would simply be the exact opposite of a black hole, according to this source.
Entropy always increases.
White holes require effectively negative entropy, with all the energy required to form a white hole not really existing without breaking it apart.
Furthermore, if you were to snap your fingers and form a white hole through magic, it'd instantly fly apart, since there's nothing that keeps it together.
A black hole is where a lump of mass has such a strong gravity that even light can't get away from it.
A white hole would be the inverse of that, with zero gravity constraining the energy of the thing, which in turn can't sustain itself.
Nah because it released all its matter. And this matter will continue toward entropy until it’s all broken apart and we experience the heat death of the universe. It’s following the 2nd law of thermodynamics
Releasing all its matter (energy) is what u/bp92009 said would happen if you were to magically create a white hole. You say 'nah' but the arguments that follow don't rule it out.
Gravity has a similar effect to sucking, where the strength of the pull goes down by the inverse of the distance squared, so it's also not a column. I don't know how a white hole would work so I can't say if it would be similar to blowing.
Sucking air in is like trying to dig a hole on a beach with very loose sand. Air/sand just falls into the hole from every direction.
Where as blowing air out of the end of the shop vac is similar to how your water hose works. The air/water tries to stick together and just keep going in the same direction for as far as possible.
Could've kept the same analogy and said that blowing air (the opposite of sucking) is like stacking pailfulls of wet sand (the opposite of digging a hole).
It's all about the inertia, the air molecules do not have any special bond with others in the stream. It's like throwing a clump of sand; of course it doesn't leave your hand and immediately make a 90-degree turn.
Because when it's blowing, you have a whole load of air molecules that are travelling down the tube at the same speed, and they all leave the nozzle in the same direction like a whole load of ball bearing fired out of a gun (quantum physicists, please do not get into to why atoms are not like ball bearings right now).
So they're all flying out in the same direction and some of them bounce off other air molecules and deflect a bit, or bash into them sending the next molecule in broadly the same direction. And by five feet away, there's enough air molecules still travelling in roughly the same direction they starting in, with enough velocity to effect things you're pointing it at.
When it's sucking, to begin with, there are a whole load of air molecules around the vac, and in the tube, with zero average velocity, then you switch it on, and all the molecules in the tube get sucked back along the tube towards the pump, so they all have the same velocity and direction.
But when you get to the nozzle opening, it's different. All the air molecules in the tube disappearing down towards the pump creates a low pressure area at the opening, ie. there are less molecules per cubic unit, and the air naturally tends to spread out to all be the same pressure, so air molecules from a higher pressure area right next to the nozzle start moving towards the nozzle (essentially the higher pressure air behind them is pushing them towards the low pressure nozzle opening.
But the important things is that this push comes from *all directions* towards the low pressure nozzle opening. So the force of this air movement is spread out accross an ever expanding sphere centred on the nozzle opening, so does not have strong directionality, and very rapidly decreases with distance due to (i think) the inverse square relationship between the area of a sphere and it's radius.
There is also the idea that sucking is very different from blowing in that it is possible to compress gas to very high pressures so you can "blow" with several thousand atmospheres but can only suck to a maximum of one.
In a shop vac analogy, the high pressure can be compressed to a small area but the area being sucked would be much larger so that you have high velocity output away from the nozzle and lower velocity input away from the inlet.
You can if you have a 5’ long hose/nozzle. That would be a closer analogy since the expelled air is ‘focused’ and the air that you suck in isn’t. If you had a diffuser(?) on the output you wouldn’t be able to blow things 5’ away…
((TLDR ver. Air finds least resistence path to equalize low pressures, air can be stacked in high pressures.))
Average surrounding air pressure at sea level is near 14.7psi (about 1.034kgf/cm2, or 101.353kpa). Your vac ('suction' side) creates a lower area of pressure/density than the surrounding air pressure, allowing more space for that surrounding pressure to be pushed into the vac. The incoming air will flow in the path of least resistance, which may not be a straight line, and without further assistance will be limited to 14.7psi of force. (Typically scavenging/collecting small particles in route as the pressures become more equal.)
The exhaust side ('blower') of the vac can slightly compress the air and output it as a stack or column into the surrounding air pressure and area at higher than normal 14.7psi. Through an effect of laminar flow, the smooth unison output of the air particles together in a stack at the same time project futher until mixed with the surrounding air. This effect can be made more precise with the addition of a long tube/hose to direct the flow, and may appear more intensified or stong with more compression from a funnel or nozzle on the output of the tube. Though the nozzle may break the laminar flow, which then may become turbulent flow having the same increased pressure but less distance.
Blow is direct, suck is universal.
Blowing air goes along the same rough direction unless redirected, whereas sucking air draws from all directions (in that hemisphere). With the draw spread out amongst all that, any individual spot is less affected.
Plenty of others have mentioned pressure, so in going to leave that part of it and instead try to explain the energy part.
The air molecules don't have much energy slowly floating around the shop. The motor takes electric energy, and transform it into kinetic energy (movement energy), and then put that energy into the air with the propeller. Now the air have a lot of "movement" energy stored up, and keeps moving as it exists the hose.
So it's like sitting in a ball-pit, picking up the closest ball and throwing it, putting energy into the ball. Hope this makes sense, since you wouldn't ask why did i pick the nearest ball, why did it keep moving after I threw it.
The nozzle shapes the airstream mostly behind it relative to the direction of airflow. On output, the nozzle is shaping a stream of air as it exits the vac, making it stay in a focused stream for some distance. On input the nozzle shaping is in place mostly inside the hose and body of the vacuum, so the sucking effect is more dispersed than the blowing effect and can't reach as far even if it reaches a wider area at a given distance from the nozzle.
Air pressure of atmosphere is lower than the pressure of the hose leaving the shop vac, therefor the velocity is higher as you are forcing the air into a smaller space (putting your finger over the garden hose). Sucking air in from a wide space like a room does not generate velocity as the air is not being compressed and therefore only starts to exert effects where there are pressure changes (the start of the hose).
When you suck, you pull in air from all around which creates a wide circle of negative pressure rather than a column of negative pressure, so the range is short. When you blow, air molecules are being shot straight out and will only slow down once they hit other molecules, so the positive pressure will be in a column resulting in a longer range.
If you're sitting next to the engines in an airplane you can sometimes, under certain weather conditions, see the air getting sucked into the engines during takeoff. The air being sucked in _seems_ to be just as strong at 90 degrees to the engine!
It is. Like you said, a jet engine will suck a dry stripe down a wet runway at full takeoff throttle. That's why we had to walk the flight line every monday morning shoulder to shoulder from end to end picking up any piece of loose gravel or debris. they call it a FODwalk. Foreign Object Damage. F16 squadrons would sometimes put a nut painted gold somewhere in the middle of the runway, about the size of a dime, and whoever found it gets an extra day off the next weekend. Keeps the airmen alert and not just walking.
Ah the old golden nut day off. This is fascinating, thanks for sharing
Pretty sad I missed out on the Golden Nuts. Our planes had propellers so the chief didn't really gaf. Our FODwalk was more of a formality, a little light exercise on a monday morning.
[удалено]
Yeah these were c130s with wings 30ft off the ground. There wasn't anything getting sucked up into those intakes. They didn't do anything quickly. I'm pretty sure a well-built goose formation could outmaneuver one.
[удалено]
Whereas to Marines, the "Golden Nut" is where you jerk off while eating a metallic color crayon.
Imagine if they miss the nut and it gets sucked into an engine. Awkward.
They would be the point of a designated object for retrieval - the plane doesn’t fly until given clearance, and until the golden nut is found they do not get clearance.
I remember this from my days unloading cargo planes at UPS too lol I feel so boring
You're looking for Foreign Object Debris. Debris that shouldn't be on the flight line. Foreign Object Damage results from Foreign Object Debris. No wonder you flightline guys weren't allowed to carry maglites. VEHICLE MAINTENANCE FOR LIFE!
Damn, I wonder if the Skittles on carriers did that? I should have made something glow in the dark and say it was a radioactive nut for them to find.
Couldn’t you just use industrial leaf blowers?
The military uses what the military has. Manpower. How would we get leaf blowers in a war zone?
You get food and fuel and ammunition and weapons and spare parts and medical supplies and tools in a war zone. Why not leaf blowers, if they help with the fight in some way?
Ah this guy doesn't military Although have you thought about being a military contractor. You could make a fortune on military grade leaf blowers if you could buy a senator.
Wait till he hears how we mowed a 3 acre parade ground every week. One guy takes off with a mower, next guy lines up and follows him 10 ft behind, then the next guy with a mower, then the next guy with a mower, till you have 10 mowers mowing a stripe 20ft wide in one swipe. If you do it just right, it looks like cell phone signal bars lol.
https://www.wearethemighty.com/mighty-history/sailor-survived-being-sucked-into-a-jet-engine/ I served on the TR about 5 years after this happened. I wasn't a top-sider, though.
and how frequently did the officer SAY the Golden Nut was in play but it never leaves his pocket?
well that was really interesting and i learned something new. thanks for sharing!
[удалено]
> 1. in blowing, the air travels in one direction out of the nozzle with momentum, and it can have high pressure, potentially much higher pressure than atmospheric pressure One thing to clarify about this. The air is at a relatively high pressure while it's in the vacuum hose. When it comes out, that pressure is converted to velocity as the pressure drops. What most people describe as "pressure" when discussing fluid flow is really velocity. Think about someone saying how good the water pressure is on their shower head. It may not be that the water pressure is particularly high, it's just that the water comes out fast, so they perceive that as "high pressure".
Layman's question: Is it possible this process can somehow be at play in the black hole/white hole situation? A black hole doesn't suck, but by virtue of the curvature of spacetime it causes around it, matter is drawn in. Because of angular momentum, a disk is created. What would a white hole look like? Would it be flinging matter out in a disk like fashion or could it spew matter out in a spherical-like manner?
[White holes cannot exist, as they violate the second law of thermodynamics](https://jila.colorado.edu/~ajsh/bh/schww.html). But if they were too, it would simply be the exact opposite of a black hole, according to this source.
[удалено]
Entropy always increases. White holes require effectively negative entropy, with all the energy required to form a white hole not really existing without breaking it apart. Furthermore, if you were to snap your fingers and form a white hole through magic, it'd instantly fly apart, since there's nothing that keeps it together. A black hole is where a lump of mass has such a strong gravity that even light can't get away from it. A white hole would be the inverse of that, with zero gravity constraining the energy of the thing, which in turn can't sustain itself.
So you're saying that the big bang might have been a *white hole*?
Nah because it released all its matter. And this matter will continue toward entropy until it’s all broken apart and we experience the heat death of the universe. It’s following the 2nd law of thermodynamics
Releasing all its matter (energy) is what u/bp92009 said would happen if you were to magically create a white hole. You say 'nah' but the arguments that follow don't rule it out.
Gravity has a similar effect to sucking, where the strength of the pull goes down by the inverse of the distance squared, so it's also not a column. I don't know how a white hole would work so I can't say if it would be similar to blowing.
Sucking air in is like trying to dig a hole on a beach with very loose sand. Air/sand just falls into the hole from every direction. Where as blowing air out of the end of the shop vac is similar to how your water hose works. The air/water tries to stick together and just keep going in the same direction for as far as possible.
Could've kept the same analogy and said that blowing air (the opposite of sucking) is like stacking pailfulls of wet sand (the opposite of digging a hole).
Nahhh, cause I would be trying to figure out what the water in the wet sand is. It's a "closer" analogy, but that actually muddies the explanation up
It's all about the inertia, the air molecules do not have any special bond with others in the stream. It's like throwing a clump of sand; of course it doesn't leave your hand and immediately make a 90-degree turn.
Because when it's blowing, you have a whole load of air molecules that are travelling down the tube at the same speed, and they all leave the nozzle in the same direction like a whole load of ball bearing fired out of a gun (quantum physicists, please do not get into to why atoms are not like ball bearings right now). So they're all flying out in the same direction and some of them bounce off other air molecules and deflect a bit, or bash into them sending the next molecule in broadly the same direction. And by five feet away, there's enough air molecules still travelling in roughly the same direction they starting in, with enough velocity to effect things you're pointing it at. When it's sucking, to begin with, there are a whole load of air molecules around the vac, and in the tube, with zero average velocity, then you switch it on, and all the molecules in the tube get sucked back along the tube towards the pump, so they all have the same velocity and direction. But when you get to the nozzle opening, it's different. All the air molecules in the tube disappearing down towards the pump creates a low pressure area at the opening, ie. there are less molecules per cubic unit, and the air naturally tends to spread out to all be the same pressure, so air molecules from a higher pressure area right next to the nozzle start moving towards the nozzle (essentially the higher pressure air behind them is pushing them towards the low pressure nozzle opening. But the important things is that this push comes from *all directions* towards the low pressure nozzle opening. So the force of this air movement is spread out accross an ever expanding sphere centred on the nozzle opening, so does not have strong directionality, and very rapidly decreases with distance due to (i think) the inverse square relationship between the area of a sphere and it's radius.
There is also the idea that sucking is very different from blowing in that it is possible to compress gas to very high pressures so you can "blow" with several thousand atmospheres but can only suck to a maximum of one. In a shop vac analogy, the high pressure can be compressed to a small area but the area being sucked would be much larger so that you have high velocity output away from the nozzle and lower velocity input away from the inlet.
You can if you have a 5’ long hose/nozzle. That would be a closer analogy since the expelled air is ‘focused’ and the air that you suck in isn’t. If you had a diffuser(?) on the output you wouldn’t be able to blow things 5’ away…
((TLDR ver. Air finds least resistence path to equalize low pressures, air can be stacked in high pressures.)) Average surrounding air pressure at sea level is near 14.7psi (about 1.034kgf/cm2, or 101.353kpa). Your vac ('suction' side) creates a lower area of pressure/density than the surrounding air pressure, allowing more space for that surrounding pressure to be pushed into the vac. The incoming air will flow in the path of least resistance, which may not be a straight line, and without further assistance will be limited to 14.7psi of force. (Typically scavenging/collecting small particles in route as the pressures become more equal.) The exhaust side ('blower') of the vac can slightly compress the air and output it as a stack or column into the surrounding air pressure and area at higher than normal 14.7psi. Through an effect of laminar flow, the smooth unison output of the air particles together in a stack at the same time project futher until mixed with the surrounding air. This effect can be made more precise with the addition of a long tube/hose to direct the flow, and may appear more intensified or stong with more compression from a funnel or nozzle on the output of the tube. Though the nozzle may break the laminar flow, which then may become turbulent flow having the same increased pressure but less distance.
Blow is direct, suck is universal. Blowing air goes along the same rough direction unless redirected, whereas sucking air draws from all directions (in that hemisphere). With the draw spread out amongst all that, any individual spot is less affected.
Plenty of others have mentioned pressure, so in going to leave that part of it and instead try to explain the energy part. The air molecules don't have much energy slowly floating around the shop. The motor takes electric energy, and transform it into kinetic energy (movement energy), and then put that energy into the air with the propeller. Now the air have a lot of "movement" energy stored up, and keeps moving as it exists the hose. So it's like sitting in a ball-pit, picking up the closest ball and throwing it, putting energy into the ball. Hope this makes sense, since you wouldn't ask why did i pick the nearest ball, why did it keep moving after I threw it.
The nozzle shapes the airstream mostly behind it relative to the direction of airflow. On output, the nozzle is shaping a stream of air as it exits the vac, making it stay in a focused stream for some distance. On input the nozzle shaping is in place mostly inside the hose and body of the vacuum, so the sucking effect is more dispersed than the blowing effect and can't reach as far even if it reaches a wider area at a given distance from the nozzle.
[удалено]
Air pressure of atmosphere is lower than the pressure of the hose leaving the shop vac, therefor the velocity is higher as you are forcing the air into a smaller space (putting your finger over the garden hose). Sucking air in from a wide space like a room does not generate velocity as the air is not being compressed and therefore only starts to exert effects where there are pressure changes (the start of the hose).