Why this football pass seems physically impossible
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- čas přidán 11. 10. 2022
- The way a football moves through the air is almost paradoxical.
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When a football player throws a tight spiral pass, the ball glides through the air in a smooth arc, its nose pointing up toward the sky at the beginning of the toss, and then dropping down toward the earth as it lands in the receiver's hands.
The spiral pass is so familiar it’s easily overlooked as just being common sense - but it took physicists nearly 20 years to understand this trajectory.
Conservation of angular momentum suggests that the ball should not act this way. It should either keep its nose angled toward the sky the whole time or the ball should be flipping over itself as it moves through the air; but the fact that it just tips over elegantly is - to use a scientific term - weird as hell.
But it turns out the solution is easy enough to understand - as long as you have a spinning top.
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the most horrifying sentence a physics undergraduate will hear: today we stop assuming no air resistance
also why do you call it football when its clearly a handegg
no more spherical cows. now it's prolate spherical cows
The fun part is if you put a really large amount of spin on it, the slight imbalance in the ball caused by the laces can let you curve the path the ball follows. For a right-handed person the ball will curve to the right, and the opposite for a left-handed person. Also, that increased spin will make the ball almost dive downward at the end, it doesn't follow the 'perfect arch' as shown in the diagrams.
Source- I used to curve footballs around trees when people didn't believe me.
it works even easier with Nerf footballs, I think the digging in of your fingers to the ball lets you really put the rotation on it.
Even more interesting is a really tight spiral doesn't fly as well as one that's just a ~little~ bit wobbly. That explanation is one I'd like to see.
lol. I just commented something similar. I totally used to whip a football over LBs heads with a wicked dip/curve. it was nasty but my elbow aches to this day from making those types of throws. (and yes, the nerf ones were even nastier on the curve.)
Fun part: 1:01-1:02 XD
That is why players throw sidearm to get around defenders.
"It's simple enough for anyone...that's interested and paying attention...to understand"
This guy teaches students.
Average college teacher
This was a bonus question on my physics final back when I was completing my master's!
Welp…Did you pass the question or nah?…🤔😂😂👍🏿
I hope you answered it correctly.
As an amateur physicist (aka I was paying attention at school) and a football fan, I always wondered about this. Thanks for finding a pro-physicist to explain it.
I just always thought about it’s flight as similar to an arrow or dart
@@atturent Pretty sure that was how I subconsciously conceptualized it too before really noodling on the idea. No doubt the most common belief since at first pass (lol) this seems a reasonable explanation, and one we've all likely had direct experience with. However, this only works for an arrow or dart because the majority of the weight is in the front, and the majority of the drag (when not perfectly aligned to the direction of travel) is in the rear, provided by the fletching/feathers/fins/etc.
In physics terms, for this sort of passive stabilization to work, the Center of Pressure (CoP) - i.e. aerodynamic drag - must be behind the Center of Mass (CoM) as the object travels through the air. This is the same thing that keeps non-gimballing rockets on course when in the atmosphere. For an extreme example, think of the long stick on a bottle rocket; if you've ever tried to light one without it I hope everyone's okay 😂
Unfortunately, this doesn't work when it comes to a football. The reason is that a football is not just axially symmetrical (as described in the video at 1:49) but is also symmetrical front-to-back. This applies to both the shape and the weight distribution - and thankfully so, because otherwise you'd have to make sure it was the right way around before throwing it! Unfortunately, the consequence of this is that both the CoM and the CoP are always located exactly in the center of the ball. Thus it is impossible for one to be behind the other as is the case with an arrow, dart, shuttlecock, or Saturn V moon rocket.
@@atturent They do however make nerf footballs with tails & fins, and as you might expect they are MUCH easier to spiral and achieve long-distance accurate throws. To my knowledge these are not allowed in the NFL tho...
Well maybe for Tom Brady
@@atturent Anyway thanks for coming to my TED Talk
He literally didn't explain it. He just said the ball stays in line because it wants to
Whoever that physicist is he is literally the epitome of every old man professor I’ve had.
He's not a good one imo
My man was throwing the ball like the actors in all American
I’m about to say. Like, bro had to SEARCH how to throw a spiral… cmon man.
(former QB here)
I used to be able to throw a wicked pass where it would start low dip JUST over the Linebacker's heads and into my WR running a post. It was some nasty physics at the expense of my elbow. It wasn't an all the time throw but in the moment it made defenders look SILLY.
Thanks for explaining some of the science behind it. Although I was a football player for 15 years, I was a science and math nerd first and foremost. Always enjoy the content!
Liar
^^^I found Uncle Rico on CZcams!
@@southparklion not too far off. I never said I could still do that. 3 shoulder separations took a toll on the abilities.
If this holds true, then throwing in a vacuum would mean it would more or less hold it's initial angle
Artemis missions are in planning, so pitch this idea to NASA and get it tested.
Honestly shocked vacuums weren't even mentioned in this video, that seems like the obvious next step to testing the claim!
@@justayoutuber1906 ya now time to acquire a whole auditorium vaccum chamber for this "test", bigger than what nasa uses for their testing
@@TeKaMOTO And think how far you could throw the thing on the moon!
This is an interesting thought, because without the air, it would probably keep the "angle" but without air resistance on the spinning ball, it might just tumble, flip, or yaw uncontrollably, right?
"Everything is simple once it's explained." So true!
Still the best documentary channel on YT.
that still does not make it football
@@savagepro9060 ?
0:35 POV: You're taking a walk down the park and you're seeing a man being recorded throwing random groceries into the air
Vox found yet another topic I never knew I would find interesting
These videos are so informative! This is exactly the type of information that I didn't know I wanted until I saw it 🥰❤️ Thanks Vox.
Great video and excellent reporting!
Most of the world tuned in expecting to see someone explain that Benjamim Pavard pass
I was disappointed. It's handegg
or Pele, or Maradona, or Messi
@@shitmypants5275 hand me the egg
In Quebec, caught between american and european cultural sensibilities, we're so lost about what "football" is that we just play hockey.
Soccer is a sport for Women and children. No self respecting man would want to play a non contact sport.
1:07 the guys last name tho 😂😂😂
I clicked on the video thinking it’s football.. like the one played with the foot
[soccer]⚽
Did the thumbnail not tip you off?
@@pyrotechnic96 I came to the video from the mobile notification
@@mrmustangman hand egg
The important force acting on the top here is not gravity, but the *normal force* of the table pushing up on it. That normal force acts very much like the air pressure pushing back on the football.
Man never threw an object in his life. That was hard to watch.
They could have hired Joe Flacco, he is in NYC and has plenty of time on his hands. And he probably lives within a 'stones throw' of Central Park.
They could have gotten anyone else in an office full of people to throw a ball, but the writer decided he wanted more camera time to show off his lack of athleticism.
Didn't gunsmiths solve this problem when moving from spherical projectiles to bullets and rifled barrels?
yes
They didn't explain why it worked, they just knew it did
Knowledge I never knew I needed until 30secs into the video
I thought it is about angular momentum. The spin generates an angular momentum vector pointing parallel to its direction of motion. (Parallel because depending on the direction of the spin, it is either forward- or backward- pointing.)
In the absence of a net external force, it would want to maintain that angular momentum direction. Since gravity is pulling it downwards, there is a net external torque that changes the angular momentum direction.
That's all.
In the case of the top, gravity generates no torque if the top is spinning exactly vertically. When the top tends to fall off, I guess (I am being a bit hand-wavy here... so this is questionable) that gravity generates a net torque in the opposite direction the fall, hence correcting the fall and balancing it. I think this is analogous to why a moving bicycle would not fall off and balances itself.
very very interesting ..thanks for sharing
Edward, why didn’t you mention anything about the laces on the ball?
I like his ‘Light is a wave’ sign in the background!
;)
*A frisbee explanation would be cool!* The football turning from air resistance force, so that the path is colinear with it seems pretty obvious. For an alternative explanation: the rotational axis (found from Right Hand Rule) of the object wants to *balance* forces so it aligns with the acting force axis i.e. *Stability*
hence why there are more shells and fewer cannonballs to be used as explosive projectiles.
this video is the perfect exemplification that you either live or understand life, not both at the same time.
"It follows the trajectory gravity laid out for it" 🤣
Do one of these on disc golf please
Loving it 😊
bullets and artillery/howitzer/tank/canon/etc. shells do the exact same thing. those have been around longer than footballs
This reminded me of Veritasium videos. Good job, Vox!
It physically hurts me to watch this man try to throw a football.
How much change would a baseball take if it were slightly more oblong than being 'perfectly' round?
It is the same with a bullet so I don’t really understand why this would be that special
Gravity isn't "the secondary force" in the free-fall; it's irrelevant. You can imagine a gyroscope on the space station: it wouldn't wobble, but it would still be pulled down by gravity. The table pushing up on the top was the actual source of the reference axis in the first case, so when falling through the air, the ball only feels the air pushing on it.
This stuck out to me because the force of gravity is definitely much stronger than the force of the air resistance, so it can't be "secondary" in terms of strength. What's crucial is that the air resistance is pushing in different ways on different parts of the ball, while gravity pulls on all parts of the ball in the same way. Thus the air resistance is able to create a torque, a force that's off-center of the rotation of the ball.
No link to the paper in the description?
Those throws are so disappointing it reminds me of Broncos vs. Colts game.
and....... no link to the paper in the description..
Is that guy happy he took 20 years to publish?
yep
Interesting to see a football video without bashing the topic.
That's a really incomprehensible explanation.
wth...i was sitting around thinking about this the other day. I know google listens to my conversations, but this was only in my head!
So is the amount of spin the difference between a javelin landing head first and sticking to the field and a sliding belly landing?
Yes, in fact I read that javelins were redesigned in the 1980s to spin more easily and prevent so many of those belly landings.
wouldnt this be the same case for field artillery
Rule #3. Never trust a man who wears a bow tie outside a wedding
So I learned a bonus fact. I wondered how this could be explained about javelin throws or bow & arrow shots. Apparently those also spin through the air after looking up slo-mo vids of them.
Arrows also have fletching, which plays a much bigger role I would assume
Darts do the same thing. If you throw a dart without any spin, it'll just bounce off the board.
Watching this person throw things causes me physical pain.
Saying that the ball 'wants' to do x y and z is the least helpful explanation. This video did not actually explain anything but just claimed laws that the ball 'wants' to follow
Lesson 3: Believe in the spin, Johnny!
it's the way the ball is engineered
The spin is doing only one thing, stabilizing the longitudinal axis. Aka minimizing the angular momentum of the longitudinal axis. A spear thrown has the exact same. Trajectory. Because it is launched at or near the center of mass, the anguar momentum of the longitudinal axis is not changed. The tip of the ball and the spear then follows a parabolic motion. Drag has no part in changing the flight profile. Since lift is minimal.
Vox [American]: Why this football pass seems physically impossible?
Rest of the World: It's because this is NOT football
Gridiron Football. Better?
@@curiouscommand5916 Yes, anything, but football
The video is intended for Americans, and in the US everyone knows what "football" means.
@@phillyphilly2095 * not everyone
Football is supposed to be played by Foot ,not hand 😂
Before I watch the video I'm going to guess it is does its axial momentum due to its spin and due to fluid mechanical effects of the air towards the ball.
Now I'm wondering, What would a spinning top do in a vertical wind tunnel? What shape would let it stably spin? I'm guess a bullet shape
football is round...thats a rubgy ball...
Frankly, most of classic physics problems can be understood by considering the conservation laws.
This was absolutely fascinating. Seriously. I have seen A LOT of great videos on Vox. This one may be one of my favorites. I grew up watching Mr. Wizards World on Nickelodeon. I loved that show. It was and still is outstanding. This felt like an adult version of that show. Perfect
No one's gonna say anything about Timothy's last name
It's the same with the Torpedo Punt in Australian Football.
This is very interesting subject for me.
Didn’t understand it. Now I’m more confused. 😂
The angle of least resistance to the air.
I assume these are the same forces at play with a rifled bullet or artillery shell.
“Light is a particle”
Someone isn’t accepting light’s duality
Well, throwing a banana in a tight spiral did not get me on the team...but...I did save some money recently on car insurance.
Tom Brady must have travel into the future to watch this video and travel back in time to deliver those amazing spiral throws over the years for us to witness 😆
I thought the video was about football 🙂
🏈 is not Football ⚽ is.
Until I see Tom Brady try to throw a football on the Moon, I'm not convinced.
Someone: "Why does the ball stay facing the air direction?"
Vox: "Because it wants to"
Wow great explanation 👏👏👏
Does the direction of rotation impact this? Like if its counterclockwise or clockwise to the direction of travel
No, the direction of rotation is different depending on if you throw with your left or your right hand, but it works either way. Just like a top still works whether it is spun clockwise or counter-clockwise.
If you spin the ball fast enough, you can curve its path a bit and yes, the direction of rotation affects the curve direction in that case.
I want to give ' THANKS' to you guys but the option's not showing....
"What's a spiral?" - Fran Tarkenton
You mean, Sir Francis of Tarkenton.
@@damienkearns3654 You betcha!
Peyton Manning too.
This video is interesting!
(Though of course ideally the instances of the phrase “gravity pulling down” could be replaced with gravity pulling in! Towards the Earth’s center of mass!)
(Though of course, then ideally one might say that gravity doesn’t precisely “Pull” because it is not necessarily a force, and could be better described as the bending of space-time, so maybe you could say that the bending of space time, due to earths mass, sets a given object on a course towards the center of the earth’s mass…)
(though in my opinion, sometimes simplification can be useful, as long as it’s acknowledged as simplification)
Overall, thought-provoking!
At least to me!
How does Vox even come up with these questions
Timothy what
Does the same physics apply to a javelin's/arrow's path through the air?
I did some googling and found out that in the case of arrows and javelin the weighted front end causes the dip.
josh allen does not arc he just emits lasers
I feel like this is so self explanatory
Those throws literally hurt my soul. You have to use your legs to throw a football and shoot a basketball, that’s the number 1 thing I see from ppl who don’t play sports, your legs and your base matter. If you’ve never heard the term athletic stance, you want to have your legs slightly wider than your shoulders with your knees slightly bent.
same with tennis, golf, baseball
Yeah, really should have had someone who knows how to throw a spiral demonstrating as well.
Exactly a throw is about full body mechanics not just the arm but how the feet are set, the distance between the feet, how fluid the motion is, the hips, etc etc. So much goes into it.
Anything that happens in the real world that science can’t explain shows you that we don’t know enough about physics.
Two thoughts on this video
1. If I throw a water bottle in the same way, I might can do the quite epic bottle flip challenge.
2. This sport should be called American rugby, not football
I WAS JUST THINKING ABOUT THIS THE OTHER DAY
Honestly didn’t see as many comments on that dudes last name
Why did this take 20yrs? It's basically the same physics as an artillery shell.
that is not how i would throw that box of cookies..i would sling it so hard it would rip apart, and if it stayed together it would go as far a football
I threw a football for the first time in my life a few weeks ago and this exact question came to mind.
Javelins do that as well
That is not football. That is Handegg
If you trow it right it will spin that spin will make it go straight
Magnus effect.
Every who gets interested in science gets interested because of this type of teacher/professor
I don't get it. What's special with how the football is pointing? If you throw something, the front would face front while falling.
Does the same thing happen with spheres? Like a basketball?
My hunch is “no,” for a couple of reasons. First, a sphere is symmetrical in every axis, so you really wouldn’t be able to track it in the same way. Just looking at it, you’d never know it was spinning.
Since there is no irregularity to the shape of the sphere, there wouldn’t be a direction at which the incoming air pressure would align it. Any direction you spun it would be independent of the trajectory.
untouched grass science
Gotta be like Tom Brady to do it right 😂
Now do cricket ball deliveries - inswingers and outswingera
Seems like the Title should have been “… seemingly impossible to me” idk why it took this nuclear engineer so long