Why Falling Objects Are Not Always Weightless
2023 ж. 28 Қар.
120 261 Рет қаралды
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i noticed this when skydiving. you only feel that sinking feeling for the first few seconds of freefall till you hit that 120mph. it makes sense that only an accelerative force can cancel out an accelerative force. Same way you feel nothing cruising in your car. might aswell not be moving
Literally came to the comments just to say the same thing. I’ll add that to me, falling at terminal velocity feels a lot like floating in water. But with more wind. 😂
One of the interesting things about free fall is objects/people don't experience acceleration, they experience weightlessness. Whereas if you were to accelerate to the surface gravity of Earth (32ft/sec) in a car your back would be pressed against the seat. Instead, we feel the acceleration of gravity when we are sitting or standing still. Mathematically it looks as if the Earth is expanding outward.
no it is still contradicts popularized idea of certain 9,8 acceleration - we feel nothing on Constant Velocity and all of us on every ocasion feel Cｈａｎｇｅ ｏｆ Vｅｌｏｃｉｔｙ - and sometimes even miniscule change. And its hard to admit that your experience contradicts all that physic science on such basic level, so when they say: "Yea, you reaching certain speed and falls like it, due to air resistance vs, we ALWAYS SAID SO..." many will exhale with ease "ofcourse it is.." like nothing happened
@@sidjoosin6549the definition acceleration is “change in velocity” so to say we sense “changes in velocity” is identical to saying that we sense accelerations. Not clear what your point is…
@@sidjoosin6549 "Popularized idea." Way to discredit science. Yeah, the gravity is as "popularized idea" as the fact that you are a human and happened to write that immensely stupid comment.
You give the answers of those interesting problems almost no one thought of. But when you provide the answers they are amazing😅
This experiment would benefit from analog scales
Yes, an analog scale would be very good for this experiment. However, an analog scale that can support the weight of the container, but be sensitive enough to measure the weight of the feather doesn’t exist as far as I know.
Problem with analog scales is light weight objects may not measure or measure accurately. One 1/16 of a pound is 0.0625 ounces. A paperclip weighs 0.0353 ounces or 1 gm.
We don't use that A word sir. I'm offended
@@TheActionLab put the scales inside the container
@@TheActionLab Talk to a machinist........
dude you have no idea how educational you are, i thank you for everything you post your actually amazing. I’ve been watching you for so long but i feel like i finally needed to say something. Thanks a lot man!
Nice to know whenever I fall off a ladder, the ground feels pain before I do. Take that, evil ground!
😂😂
pressure is dispersed , unless working in 3rd world elevator shaft or similar, so the ground doesnt feel for you.
I just watched the vid where you had the fan and balls in your vacuum chamber and it was a lot like when you put flies in the chamber to see if they could fly, both times was concerned about your vacuum pressure and am hoping you will get the TM pump and try reaching the x10-6 range for comparison because so many people are used to that range. Your programs are the best. ❤ Always. 😁
Ooh this was cool! Never thought of anything like this before. physics is so interesting!
Also I did learn something. thank you. I had wondered about just this experiment it's interesting to note that you only see a different weight when there's a change in velocity, not when the velocity is constant, whether up or down fast or slow.
You always feed my curiosity ❤ with your interesting experiments.
A falling object will only experience the fall as weightless as long as it is accelerating, so in the atmosphere where there is drag it will quickly reach the top speed it can get doe to air resistance stopping it from accelerating anymore and not feel weightlessness anymore.
Your videos are always fun and informative!
I learned so much from this video. Thank you!
I think this is more clearly explained via displacement. The scale is measuring the weight of all of the air contained in the column. As soon as the feather displaces some of that air (i.e., is inside the column; *edit:* and is in equilibrium, see replies), the scale is going to measure the net weight (the difference between the weight of the feather and the weight of the air it displaced), regardless of if it is being supported by the air (i.e., falling at terminal velocity), by a string at the top, or by the bottom of the container.
'via displacement' Think of an ideal, frictionless perfect teardrop falling through the air, and frictionless air. It would displace the air around it, but still wouldn't exert a force down. It's a function of friction and grabbing the air, some of your weight is still transferred down through the air column. Really you probably have a small component of buoyancy as well. Start with something that is buoyant on water, and then ramp the water from water to air.
Sorry, I should've been more clear that the terminal velocity condition is still critical. The teardrop shape would still register the full weight as long as it had time to to reach terminal velocity, because that's the point when its full weight is being "supported" by the air, even though it's still moving downward. But regardless of its buoyancy, once it reaches equilibrium (terminal velocity), it is being supported by the medium and its weight (or technically the difference between its weight and the weight amount of medium displaced) will be registered. This might be easier to demonstrate with a more dense gas.
@@MasterBunnyFu 'once it reaches equilibrium (terminal velocity)' An ideal teardrop in ideal air would have no terminal velocity, it would simply keep accelerating.
Actually, I suppose the equilibrium / terminal velocity condition is the more important thing, but I think that at least buoyancy helps give a better intuition about why the weight registers and could be leveraged to demonstrate it more clearly with different setups. It would be interesting to use a higher density medium and various density objects and set it up in such a way that you could actually record the weight over time and show it approach the final value as the object approached its terminal velocity.
@@ModelLights "Frictionless air" means non-interacting and is essentially equivalent to a vacuum. As long as the object has any buoyancy in the medium, it will have a terminal velocity, since that's just the point where the acceleration due to the buoyancy force equals the acceleration due to the gravitational force. For neutrally buoyant objects, the terminal velocity is zero, and it increases as the negative buoyancy increases.
I'm curious how quickly this force spreads out if its not stopped by plastic walls. Is it an inverse square law, or something more complicated because of fluid mechanics?
comparing the air model to the water model and how they function the same also shows how gases are fluids, basically showing how the higher density matter (feather) is displacing the lower density matter (air)
I feel like I missed something you were pointing out at the beginning because you didn't mention it again for the rest of the video. What was the distinction in the closed tube when you used the laser?
The laser was just a cool way to cut the string through the plexiglass without possibly skewing the results by physically touching it.
Today I learned something new! Thank you! ✌️
One thing I would do different about the drone inside the bin with the scale is you probably need a bin the same size as the outer bin on top of the scale and you could register the entire weight of the moving drone. But if it still works otherwise then that's cool.
That was very interesting. Thank you 👌
You should do same experiment with copper tube and Magnet it will be awesome and you will get correct weight and time to capture the weight difference
Thought the first part that you would measure the weight feather was falling since its trapped. Great explanation tho 👍👍👍🔥
I have a question related to fluid mechanics. Q:-) If I have a container of given dimensions with water filled upto brim and placed on frictionless surface . After filing water I open the hole at bottom of container as a result it moves forward. Then Can we find the velocity time function for the container. And total displacement till water ends . Assuming area container >>>>>> area of hole.
Enough downward pressure to cause pressure sensitive adhesives to stick, w/o actual mechanical contact pressure being applied?
One final experiment was needed to seal the deal for good: to demonstrate that when dropped in vacuum, the feather weighs less the same amount as the steel ball.
nasa did this in the moon landing
@@atrckr-bf7de I know, but still this could've been easily included with these experiments in this video.
Great episode! People will always get mad if something you claim goes against their assumptions about reality. There even seem to be a strong correlation between how well you prove your point and the level of anger you manage to provoke. When a small part of your audience gets really riled up, and use strong wording without valid argumentation you probably did a very good job of enlightening most that that were receptive, and didn't know already. With the views you get, if only a few people gets upset when you explain and demonstrate so well, I'd consider it mostly a sign of well chosen subject.
That’s a great insight! It explains not only the anger of the flat earth crowd, but also the current “anti-woke” politics in the USA, and also the vicious attacks on vegans. Some people don’t like having their preconceived ideas proven wrong.
@@jpe1in fact people will dislike literally everything especially on the internet for no reason
Another interesting video, I was just watching your old giant magnet videos.
Is being in a contained chamber causing interference from heightened pressure and turbulence not allowing unlimited air expansion compared to if this was done in the open? so basically Is the gravitational force equally transferred to the downward force of air resistance? Is weightlessness while in free fall actual weightlessness or is it just a perception based on the view point?
so the air moved by the feather has the same momentum as the feather therefore it gives the balance reading of the mass before it reaches it?
Is what happens to the scale very different from a pressure wave, propagating from the feather, like wind or sound ?
it's exactly that. the feather pushes the air, which in turn pushes the scale
The feather pushes the air molecules below it downwards. This then pushes the air molecules below them down. And again and again until the bottom molecules reach the scale - aka a pressure wave.
The coolest display of a feather dropping was by Commander Scott on Apollo 15.
Was great that they did it in such a quick non-chalant way just to quickley demonstrate to the masses without getting super scientific. Was over in like half a minute, lol.
@@louf7178 I've often wondered why those who try to counter the moon landing deniers don't use this footage more often. Firstly, to work at all everything in the image has to be in vacuum - no mean feat to get a vacuum chamber that big - and secondly you can work out the gravitational constant from the time taken to fall. Of course that will match the moon's gravitational constant.
@@mb-3faze Was thinking that just as I was replying.
I could be wrong but as long as you have a container that only has an opening at the top, once the feather enters the tube, the "cup" would weigh the weight of what was "in" the cup, in this case the combined weight of the feather and the air, and since the air has been tared out, just the feather. But since the feather was suspended by external force prior to laser cutting, that weight wouldnt register until the string was cut and the feather was only supported by forced inside the cup.... thats less pussing down on air molecules as opposed the measuring the weight of the closed system.
Where people are getting tipped up is that they don't understand that in order to be weightless you have to be constantly accelerating. Terminal velocity means you are no longer accelerating.
So, if I stood directly under a parachuter, would it feel like they are standing on my shoulders? And at what distance would we feel it?
let's say you hover with a drone above a pipe to redirect that airflow sideways so that the air doesn't push on the ground but instead parallel to it while covering the pipe inlet or outlet and then remove the cover: can the drone still hold its position or does it fall down? yes there are friction effects from redirecting the air in the pipe, but is the loss of counterforce noticable?
Once the drone throws the air down, it doesn't matter what happens to that air. It has no effect on the drone. Once it pushed off the air, it already gained its upward force. You can see something similar in this video: kzhead.info/sun/l89xnaqQq2ubhnk/bejne.html
@@TheActionLab so the drone is not relying on the floor pushing against the airflow. you showed that hovering right over the scale you can measure the force of the airflow. i guess suddenly removing the floor by opening a way for the air to escape will not change the behaviour of the drone because it doesn't need the floor, right?
Man, I'd kill to have a time machine and you as my physics teacher, it's straight up infinitely more educational to have both the theory AND visual.
This cannot happen because if you made the time machine to get him to be your physics teacher, you would've never made the time in the first place. But you need to make the time machine to get him to be your physics teacher
I was expecting that there be some effect to air/gas being compressible, versus something like water that can't be compressed. For example, if we use low air pressure, maybe only part of the weight will register?
It doesn't matter if the medium compressed or not, once it's compressed enough it will transfer the force
It's like the air hitting you in a subway station when the train it coming. The moving air exerts a force.
What happens if you drop something with minimal air resistance? Like a sharpened pencil?
Hey action lab, I have a question I hope you can clarify. A Mr Ken Wheeler, states that all sides of a permanent magnet have 2 poles present! First I know this guy is his own cult of personality, but I did a series of tests, & and low and behold, my tests seemed to show he was correct. But just because a thing seems true, doesn’t mean it is, so I’d love it if you’d test my tests/trails, and see if you agree. “This would explain why a monopole effect can not be made by moving the poles a great distance apart, which we all know doesn’t work. But if I’m right(and K.wheeler), then a monopole like emergent effect may be possible. Ken’s claim, that like poles do not repel (at least in the center of the N & S ends, that most believe to only have 1 pole present, he stakes a smaller disk magnet, like poles towards each other, then it sticks to only the center of a monster magnet disk, and does remain, this I have tested with smaller sets of 2 different size disk magnets, and it did as he states, then I tried to place the smaller disk magnet to the larger one, with opposing poles, it will not stick to the center area, and is attracted to the other 50% of the end of said, so I tried it with various powers of magnets from cheap ceramic to N35 & N52, to see if maybe it was sticking to the center because it was a weaker field there. It absolutely seems to be correct. And this would also explain why one can not magnetize a pointed cone or pyramid shape permanent magnet directly do it center to its cone without the field shifting to the off center, because both pole can not be present on the cones tip. As you know a cone or pyramid shape that has the top cut off will not shift, & can be magnetized through its center, & said top point can reach up to 1 Tesla ( unheard of prior in permanent magnets). I also tried testing hanging metal rods from various parts around and it’s center, it did not seem to be the case of said attachment being due to a weak spot/s in the field! It does seem that there is both poles present at the n & s end caps, but they are not easily noticed because one covers the other pole underneath!... Have I just missed something so obvious and fallen prey to a untrue belief? Or is this true? I can provide diagrams of exactly what I am speaking of if it is confusing! Thank you, please help, trying to learn the truth. Some of Mr wheeler’s other absolute stuff I have found to be unprovable, but this I can not seem to debunk... Now here is where I have a issue, we can magnetize a small straight pin tipped at both ends, but like the cone or pyramid with a point, it may just be shifting its alinement slightly off center from the tips(I suspect but is hard to test)... Please help
This reminds me of the old thought experiment about a box truck that is carrying a load of live chickens. If all the chickens in the box of the truck started flying, would the weight of the truck go up, down, or stay the same?
Same, cause the birds are supported by the air inside the box.
Is the momentum transferred through the air at the speed of sound?
Sir, could you try another version with underwater scale, and falling object in the water? Non boyant objects of course
He did that. He showed the skydiver without the parachute falling in a graduated cylinder filled with water
Oh i see what you mean, the scale underwater. A regular digital scale likely wouldn’t survive being underwater
Just for fun. If you put the feather in a vaccume chamber would it reach a faster terminal velocity?
In vacuum and on earth it will keep accelerating until it reaches the center of the earth .
Think of a perfect teardrop with no friction or air resistance, falling from top to bottom. It would fall freely, and exert no force upon the column of air as it falls. Everything less perfect is exerting some of the force of gravity working on it against the column of air, so some percentage of its weight should register.
What if you dropped an object that threw part of its mass immediately below it as it was falling?
If it were in a vacuum would it register the full weight at the top instantly at fall or will there be a second to reach terminal velocity from the stand still? And if you had a scale that reads in nanoseconds
In a vacuum, there is no fluid that will introduce resistance to falling object. This means that the force acting on the object (earth gravity) remains constant, and the object it will constantly accelerate. This results to an object not having a terminal velocity.
@@d4slaimless I was asking if in a vacuum would it always read the full weight or no weight because there is no terminal velocity/ no air, and then on top of that if you had a change and could have super fast readings would you measure any weight difference?
@@scottbattaglia8595, well, since there is no fluid to transfer the interaction, the scales should not register the weight of the falling object. Until said object drops on them.
@@d4slaimless so performed in a vacuum it would register no weight till it hits the scale?
@@scottbattaglia8595 It seems so to me.
you should do a video of areogel in a vacuum chamber i have seen nothing about it on google
Have you gotten and shown some dry water yet? thats some crazy stuff.
Bruh, that's one of his classics
Cool test. But your explanation could be improved. The momentum is only transferred to to the air directly under the feather, not all the way down. That air will subsequently flow to the side and around the feather to the top to equalise the pressure. However, that momentum increases the pressure under the feather a tiny bit (compared to a feather that is suspended mechanically). That pressure puts a downward force on the underlying air, which eventually reaches the scale through the intermediate air molecules.
does this still work without the air?
And if in a vacuum, does the steadily falling feather have weight before landing?
Also, if a guy is in elevator shaft , bottom floor, basement, whatever, and the elevator of that shaft has reached terminal velocity falling downward, not upward , though that would be cool, ( maybe ones in Dubai are capable) plummeting toward guy, when does he feel the full weight of elevator prior to being squashed, or miraculously not being squashed (even cooler)?
theres som " compress" puns available in this scenario but im not going to force it.
Does this mean that if you have a cage high enough to drop a heavier object into, and that object reaches terminal velocity, we'll be able to measure the weight before it hits the scale?
yes, it works at all scales
would you break ice without contacting it if it cant support u
Thank you.
so, will the weight change when you drop it in a vaccum?
Semi reminds me of a trick science question : If you are fired from a cannon at what time in your free trajectory do you experience zero gravity. 1. On the way up. 2. At the top. 3. On the way down. 4. All the time. The answer is 4 I think, but anyone who's been on a rollercoaster will intuit 2 "at the top". Question clearly doesn't account for air resistance though. This is starting to sound like a new RollerCoaster design, maybe I should patent it.
Why? The only moment where you have no net acceleration in the up/down direction is at the top(?)
@@whuzzzup true, but if youre shot from the cannon at an even somewhat horizontal angle, when you hit the peak of the arc vertically you would still be decelerating horizontally so would that still be considered/feel like freefall?
At the very moment you reach the top, your acceleration in any direction would be zero which means you would perceive the same weight as standing still on the ground, 1G. You would then immediately begin accelerating toward the ground though and, on your way down, you would perceive zero gravity until you reached terminal velocity and returned to 1G so the correct answer would be 3. It is definitely a weird trick question that I can see a science teacher posing but I’m not sure really what point they were trying to get at because 4 doesn’t make sense at all. Maybe the 4th answer was actually the opposite of what the OC remembers, “never”. Technically, gravity is always acting upon you here on earth and it’s just your perception of “zero gravity” when you are falling.
@@whuzzzup There's no difference between the top and up/down. G is the same at all times, when going up, it is decelerating you, when going down it is accelerating you, at the top it is just acting on you. You are in free fall the entire time, your relative velocity to the surface of the earth is irrelevant (I think is the point). For reference see the vomit comet, the weightless period starts in the upward coast and ends in the downward coast when they power the engines back up.
@@Bystander333 You seem to be correct. A free fall seems to be defined as a motion where gravity is the only force acting on it - I never really thought about it that simple. So yes in this case all parts of the flight (without air resistance) are free fall.
Art Globes is here it's at. Its so fascinating.
How is your explanation different from the one given at 2:55? They said the parschute traps the air, forcing it down the walls and into the scale You said the feather pushes down on the air, forcing it down the walls and into the scale It's the same explanation?
Would it do the same under vacuum?
No, it shouldn't. No resistance from the fluid (air), no drag - means no terminal velocity. Nothing to transfer the force.
One assumes you are not going supersonic. Terminal velocity would be much weirder in that case
love the videos but could u make em a little longer?
That was very interesting 😊😊😊
Interesting! What about something very dense, like a cube of Uranium falling from the sky?
I guess you could still have something fall at terminal velocity without measuring the weight. The force downward will travel at the speed of sound. So there will be a delay before the scales pick up the force from the air. In the case of the drone, if the drone and the jar were in freefall. The drone would exert a force on the jar pushing the jar downwards at greater than g. The combined center of mass of the system would be unaffected. The drone would hit the top and be acellerated downwards. Cancelling out the extra push from the drone (the jar would move at less than g for a brief period). Then both would travel at g assuming the drone sticks to the top of the jar. Overall the combined center of mass would travel at g for the entire duration. Ignoring effects of air outside the jar. I probably shouldn't have written this all out but I can't bring myself to delete it now. Nobody asked for this. Anyway I bet there a super janky way of measuring the speed of sound as the delay between the mass and the scale. Thats the thought that got me writing all this. Its a lot like relatively but it isn't the same as relativity.
Does a colder ice cube melt faster?
I think your channel is big enough for you to hire a good animator. It would make things much clearer and more fun
i'm gonna claim that the weight you measure isn't true weight, rather, (the force of overall drag) - (the force of drag produced by draft) a very small difference, but i couldn't see how force produced by draft, could be transferred to the scale. sadly, i don't think there is instrumentation sensitive enough to measure this :(
so if you use a super strong fan blowing toward the scale, it would register the weight👀
I click on your videos because you always teach something new
If you are ever unlucky enough when you car brakes down on the highway you can feel air from the other cars shaking your vehicle from how quick the amount of air they are pushing out of the way! And also basically if a sonic boom where a firework anything else would fall below.
good video, well explained. I didn't feel angry at all XD
you had me at, "I'll cut the string with a laser".
what is a skell?
Theoretically, could we catch a free falling human at terminal velocity if they landed in a tube? Could that dragged air somehow serve as a buffer to slow the human’s momentum?
Assuming there was a good seal between the falling person and the walls of the tube, yes. It’s a similar principle to how an air shock absorber works. The person would act as the piston and the trapped air molecules under them would be forced to compress. Also, the friction between the person and walls of the “cylinder” would be a big factor though.
There have been examples where the fall of a falling elevator was slowed down by the air getting compressed under it in the elevator shaft slowing it down considerably.
That globe place should make a cmb globe.
They should restock before starting a sale
Are you still an active LDS?
cheap scale, by a high precision one downto 1 or 0.1mg, and replace the draft shield with the ones you use
Idea: get an Arduino based high precision scale, so once connected to a computer you can make a graph and have a much higher reading speed.
mmmm.... in my point of view the "system" contsitued by the tube the air and the steel cube should be equal by in mass and in weight (which is mesure when the steel is attached and when the steel is free falling... your results only shows the fact that the box is not sealed... so your intitial proof is puzzling for me... the system don't loose weight, therefore it shouldn't move (except perhaps at he beggining, due to the opposite accelration... but in my opinion if your tube were longer and air proof , you should see O on the scale before the steel hits the bottom
It doesn't matter if it is sealed air tight or not. That changes nothing. There is an internal acceleration happening, and during that, the weight of the whole system changes. Once the acceleration is stopped then the weight goes back to normal. Think about it. You can change your weight momentarily by jumping or raising and lowering your torso with your knees, that is because a portion of your body is accelerating. Anytime there is an acceleration in a closed system the weight of that system changes, until the acceleration stops.
ohhh thats why you talked about terminal velocity... when its reached, theere is no more accélération... so the weight comes to normal.. iI think i understand now thanks. @@TheActionLab
So. Are you saying if I’m walking down the street in NYC and a piano is about to drop on me from a ten story building, I’d feel a fraction of the piano’s weight on top of my head before it lands on me?
So if someone is below a drone/helicopter they feel the weight of the entire chopper?
This is kind of like why a helicopter will decelerate right before it hits the ground. When it gets close to the ground, inertia pushes against the helicopter there is less space for the air to move freely underneath the helicopter and therefore it is like a cushion before it even touches. Are they still mad at you?
What would happen in a vacuum chamber? Would it not register any weight?
Scale should show -0.08g (I think).
What happens in you mix vantablack, musou black, and BLK 2.0 together? Will you make the darkest paint in existence????
why did you cut your hair tho. good video
I looked to see when I subbed and it was 5 years ago, the toilet paper dispenser. Same time as Backyard Scientist, Brusspup, NightHawkinLight and Cody's Lab. Before that it was VSauce, Minute Physics, 60 Symbols. Before that, Casey Neistat, The Art Assignment (Mrs. John Green) and Smarter Every Day. Been a good 10 years.
You went cheap on us. 😂 If you had paid just $15 more for the scale, it would have given instant real-time measurements. But nooo. You thought all digital scales were the same. Just kidding. 😂 Great experiment man! Love your channel.
Which is heavier. A pound of air or a pound of feathers? This has haunted you all throughout life . Here, have a cookie 🍪
See if you can turn the vacuum cube into a battery, i.e check its energy density and compare it to modern batteries.
It is the ground effect like when a helicopter flies close to the ground it lifts more
i had no idea that this would be true
Are you related to Davie from April and Davey? On KZhead
The feather is reading on the scale for the same reason that a helicopter will not change weight whether it's hovering 6 inches above the scale or planted firmly on the scale.
This makes sense, it's similar to how boats displace their weight in water when moving, I think.
"For our next test we are dropping a baby off the eiffel tower"
So by this logic, if a mile wide asteroid hits earth or a city on earth. The city would be squashed or under its weight before it ever hit?
Maybe a miliisecond before impact, but since the air isn't contained in that scenario the air would compress and rush out the sides at great speeds.
don't tread on me t-shirt 😂😂😂
Adding smoke to the box will help to visualize air movement.
amazing
...that's an interesting 'snake-on-yellow-backdrop' shirt you have there Looks like the snake is somewhat alarmed though, perhaps some careless person trod on it beforehand