Why Do Spinning Things Do This? - Smarter Every Day 312

0:00 It's finally time for the flying saucer video.

0:02 No, I'm joking.

0:03 Welcome to Smarter Every Day.

0:06 This is a YouTube channel that I...

0:08 My name's Destin.

0:09 I make little experiments sometimes to try to understand things.

0:14 There's a thing that I want to understand that, if I'm honest,

0:18 I have pretended to understand it in the past, but I don't think I really did.

0:22 That thing is gyroscopic procession.

0:25 I know how gyroscopic procession works.

0:29 If If you touch a thing on one direction,

0:31 it happens 90 degrees out of phase if it's spinning.

0:34 There's been a lot of explanations on the internet,

0:36 and most of them involve a bicycle wheel.

0:39 I've got friends that have made videos about this.

0:41 You can see professors use a bicycle wheel to explain gyroscopic procession.

0:45 I've even made a video using a bicycle wheel

0:48 with my friend Carl trying to explain gyroscopic procession.

0:51 But what I explained is what happens, not why it happens.

0:56 I think a lot of videos, mine included,

0:59 kind of assume a lot of prior knowledge, and they jump from zero to 10.

1:04 But what I need is a baby

1:06 step towards understanding about gyroscopic procession.

1:08 So this video today is for me.

1:10 I'm trying to understand this, and I'm happy that you're

1:13 here because I have a crazy setup in the garage,

1:15 and I'm going to show it to you now.

1:17 First of all, this is the garage, and I have cameras everywhere.

1:22 I'll just show you the cameras.

1:24 Got a camera here.

1:25 Is it on?

1:26 Are you on camera?

1:27 Yeah, that camera's on.

1:29 Got a Got a camera there.

1:31 Got a camera there.

1:33 Got a camera here.

1:35 Got a camera down there on the floor, and got one way over here.

1:38 Okay?

1:38 So what you'll notice is I've got an arrow in the floor,

1:42 and that represents the direction that this model of a disk is going to fly.

1:49 If I were a big person and I could throw a frisbee

1:53 or a disk like this, this is how the disk would fly.

1:58 And the reason we're making this video is because

2:01 I'm doing a series on how disk golf disk fly, and I want to understand it.

2:05 I came up against this problem where

2:08 gyroscopic procession is involved, hard to even say.

2:10 And I realized I didn't understand it.

2:12 I built this model, and then I realized this video needs to be

2:15 its own video because I haven't seen an explanation like this on the internet.

2:19 First of all, let's look at this disk.

2:21 If I have just a disk suspended from these four wires that you can see,

2:26 one, two, three, four, I've got a bearing here so things spin.

2:30 But what would happen if I just take my finger

2:32 and I push down on this disk right here?

2:35 So this camera is 90 degrees here.

2:38 I'm throwing it that way.

2:40 What happens if I push down on this?

2:42 Ready?

2:42 One, two, three.

2:43 Okay, it just tips.

2:45 No big deal, right?

2:46 No big deal.

2:48 So now let's look at gyroscopic procession.

2:50 Let's look at what happens when the disk is spinning and I put a force there.

2:54 Okay, let's do that.

2:55 And the way we're going to put the spinitude

2:58 in this is I have 3D printed that thing,

3:02 and I have the disk, Spinomatic 3000 here.

3:07 And what I'm going to do is I'm going to put that little

3:09 silicone paint stirrer that's my last of three because I broke the other two.

3:13 We're going to put that in there and we're

3:15 going to We're going to slowly add spin to this.

3:18 Another way to say this is we're going to increase angular momentum,

3:22 but we're not going to use the physics words here.

3:24 We're just going to spin things.

3:26 Okay, so spinning this thing up I've learned that if it's

3:31 bent like that, then I can go faster once it straightens out.

3:36 All right.

3:37 Caught up to me.

3:40 Catching up to...

3:41 All right, there it goes.

3:45 All right.

3:47 All right.

3:48 One of the hardest parts is to decouple.

3:52 Okay, hold on.

3:54 Okay, we have decoupled.

3:56 It's very stressful.

3:57 I've broken two of those so far.

3:58 Okay, so we now have a spinning disk with a lot of angular momentum.

4:04 Let's do the same thing as before,

4:09 except this time we're going to push down with air right here, okay?

4:14 So Is it going to do the same thing it did last time?

4:17 Let's watch.

4:18 Got a 90-degrees angle here.

4:20 Watch what happens.

4:22 Three, two, one.

4:24 It does not.

4:26 It does not do the same thing.

4:29 If you were watching, I pushed down here with the air,

4:32 and that side over there went down.

4:37 So 90 degrees after the applied force, it went down.

4:42 You'll notice it's doing this wobbling thing now.

4:55 The more experienced of you out there will

4:58 note that this this is actually gyroscopic procession.

5:02 Yes, you're right.

5:03 That's a function of how I have my device set up here.

5:07 But I think it's neat that we apply the force here

5:11 and it saw something happen 90 degrees out of phase over there.

5:17 Let's do it one more time, and then I'll show you one other thing.

5:22 We're going to slow this down, quit the wobble.

5:27 This time I'm going to push up,

5:28 and I'm going to let you think about what's going to happen.

5:31 Where's my drill?

5:32 Okay, here it is.

5:38 Decoupling?

5:38 All right.

5:39 Man, that's like refueling an airplane or something.

5:42 All right.

5:44 We've got our angular momentum applied.

5:47 This time, I'm going to push up right here.

5:50 Okay, and so if I push up, gyroscopic procession says that whatever I do

5:55 here is going to happen 90 degrees later.

5:57 If you just watch the first second and a half

6:00 before all the friction and stuff takes over.

6:02 Watch what happens.

6:03 Ready?

6:04 One, two, three.

6:07 You can see it lifted on that other side.

6:10 It's not exactly 90 degrees.

6:12 I've got some problems with my setup,

6:14 but you can see it's not lifting where I'm blowing the air,

6:17 which is what it seems like it should do.

6:19 This is what's happening.

6:20 This is a way of thinking about what just happened.

6:22 I pushed on the bottom of that thing with air right here.

6:29 We're right here, but the displacement of the disk was actually over here.

6:36 So I had this lift vector here,

6:39 but the displacement didn't happen till way over here, right?

6:44 And if you look at that from the top down.

6:46 That's pretty weird.

6:46 Isn't that weird?

6:48 Why am I pushing here and a thing happens over here?

6:51 This is the part that I'm super excited about.

6:54 This is an explanation that finally my buddy told me about this, and it works.

7:02 Here's what we're going to do.

7:04 We are going to ignore angular rotation and angular momentum.

7:08 Those are big words that are intimidating.

7:11 We're going to look at plain old linear momentum.

7:13 That's what we're going to do.

7:15 I've got this camera here.

7:16 You're now on that tripod up there.

7:18 I'm going to talk to you right here, and I've got this cue ball here.

7:22 So what I'm going to do is I'm going to grab this number five ball here.

7:28 And what I'm going to do is you know how pool balls work, right?

7:32 If I have just a ball sitting right there.

7:35 Let's zoom in on that.

7:36 If I've got a ball sitting there and I want to roll this other ball into it,

7:41 there's a momentum transfer there that happens, right?

7:45 Let's do it one more time.

7:46 I'm going to roll into it.

7:48 Whatever angle it hits at, it's going to go off at a different angle.

7:51 But let's look at what happens when this thing is rolling.

7:54 If I have a ball, this five ball is moving from right to left,

7:59 and then I hit it as it goes by, look at that, it goes down at an angle.

8:03 Did you see that?

8:04 Let's try that one more time.

8:06 I'm going to roll it here.

8:08 Five ball coming across.

8:10 I hit it, goes down at an angle.

8:12 The ball rolls in and it has just velocity in this X direction, right?

8:18 It's just going in that direction.

8:19 This ball comes in and hits it about right here,

8:22 and it's got velocity in this Y direction.

8:25 So we've got momentum in X, momentum in Y.

8:27 And then what happens is you get a resultant momentum.

8:31 And that resultant momentum is that ball going off at an angle, okay?

8:34 So the system remains the same.

8:37 So watch, all the X that I put in and all the Y

8:40 that I put in, it stays the same even after the collision.

8:45 Okay, that's interesting.

8:47 Okay, so here's what we're going to do now.

8:49 We're going to go back to our other

8:51 little thing that we were looking at over there.

8:53 Let me get you off this tripod.

8:55 Let me bring you back over here, and I've got a trick for you.

8:59 I think this This is really neat.

9:00 Okay, so if you think about our disk,

9:03 our model of the Jolly Green Giants Disk golf disk or whatever this is, right?

9:09 All it is basically is its mass out at a radius from a pivot point.

9:15 That's all it is.

9:16 Smart people will know how to calculate the moment of inertia as MR²,

9:22 or in this case, it's going to be somewhere between one-half MR² and MR².

9:26 But what if we replace that mass at a radius with pool balls?

9:34 Just like that over there,

9:36 we had that little situation where we had linear momentum.

9:40 What if we use the tool of linear momentum

9:43 to think about this rotational momentum or this angular momentum.

9:47 It'll make sense in a second.

9:48 Remember, I've got a camera over there looking in the direction of flight,

9:53 indicated by the arrow on the floor there.

9:56 That's where the red ball is right now, the number ball.

10:00 We also have this blue one over here.

10:05 And then we've got this camera that's looking 90 degrees off, right?

10:08 So I can do the same thing as before, okay?

10:11 I can rotate this thing up.

10:13 But what I want you to do is just think about this reference frame.

10:18 This camera right here is the most important camera in the whole place.

10:22 So what I'm going to do is I'm going to rotate it up again.

10:25 Let's do this.

10:27 I'm not going to rotate this as fast because

10:29 I've learned I learned that lesson the hard way.

10:32 Don't worry about it.

10:33 It was crazy.

10:34 So I'm rotating this thing up a little bit.

10:36 I'm going to decouple.

10:37 So now think about this camera as the same thing.

10:43 I've got a ball coming in from the right going to the left.

10:46 And what happens if I roll another ball down and I hit it?

10:51 What happens?

10:52 You're just thinking about this camera.

10:54 It goes down at that angle like we talked about earlier, right?

10:59 So if you think about it, if I've got an X component of momentum,

11:05 I've got a Y component of momentum, I get a resultant, right?

11:10 I'm just looking at this 2D plane right here on this camera.

11:13 But that's not where we live in right now.

11:15 We're living in a rotational reference frame, and we're connected to this stick.

11:20 So if it goes down, it's got to go down like that.

11:25 And that means that ball up there goes up.

11:28 And then once we get like that, well, there's nowhere to go.

11:31 We have to continue rotating like that, right?

11:34 So I like to think of this whole thing as a linear momentum problem

11:39 that manifestsates itself in some weird gyroscopic wobble

11:44 that only really smart physicists can understand, right?

11:47 So watch again.

11:48 We're going to rotate.

11:49 I'm going to go a little faster if I can.

11:53 Going to rotate.

11:53 I'm going to come in.

11:55 I'm going to try to drop it.

11:56 I've missed it a lot.

11:57 Look at that.

11:58 About 90 degrees.

12:04 That's something I want to think about.

12:06 You notice it wobbled in a really bad way after the fact.

12:10 That's because I've got friction here.

12:12 That's because this is an imperfect demonstration.

12:14 I've got this pendulum,

12:15 and there's this other thing happening here that's hard to explain.

12:19 But for now, this is just a tool that lets me

12:24 think about the effects of gyroscopic procession in terms of displacement.

12:29 That's what this does for me mentally.

12:31 We have that.

12:33 Let's go back to the disk.

12:36 If I were to put the disk back on there, let's think about it like this.

12:43 We're going to start.

12:44 The reason I'm doing all this is because in this disk golf disk video,

12:49 I realized how much gyroscopic procession plays into rotational dynamics.

12:55 When I finished my master's degree in mechanical and aerospace engineering,

13:00 I left the room and I went outside

13:02 and I looked up and there was a helicopter flying,

13:05 and I realized I have no idea how that's working.

13:08 And so I'm guilty of a lot of time thinking I know things,

13:11 but I don't really understand them.

13:12 And so that's why we're doing this, is because I

13:15 want to understand it in a way that I haven't before.

13:17 So let's go back and think about this spinning disk.

13:20 Okay, so I'm going to spin the thing again,

13:22 and this time I'll spin it that way, and we'll blow up this time.

13:27 Okay?

13:27 So I'm going to get it going.

13:29 Let me, this is fun.

13:30 Let's just get another camera here just because it's fun to watch this part.

13:36 It's really hard to see.

13:38 All right, so here we go.

13:41 Let me get this going here.

13:45 I always have to concentrate a whole lot here

13:49 because I could do things like that and break things.

13:53 All right, I feel like I'm docking with a spacecraft, in interstellar.

13:56 Okay, so now we've got this thing moving.

14:00 And now what I want you...

14:01 It's rotating that way.

14:02 I want you to think of it not as mass, but as a bunch of billiard balls.

14:06 And we're going to come in with the air, and we're going to hit it right there.

14:08 So what's going to be the effect?

14:11 If we do that...

14:13 No, let's go up.

14:15 Let's say I'm going to hit it with a billiard ball going up.

14:17 Let's just change it up.

14:18 What's going to happen?

14:19 If I blow up here, it's going to go what?

14:24 It tilts up on that side over there.

14:26 Now, it's not perfect.

14:28 Let me slow it down.

14:30 It's not perfect because I've got a lot of friction and stuff there.

14:33 Oh, I just marked up the top of the thing.

14:35 But you get the idea of what's going on, right?

14:38 With gyroscopic procession, if it's rotating,

14:41 if you apply a force in one location,

14:44 the displacement actually occurs in a lag-type way, 90 degrees out of phase.

14:49 It's a really interesting concept, this gyroscopic procession.

14:53 A lot of the explanations that you'll

14:55 see on the internet involve a bicycle wheel.

14:57 But if you go back and you look at the bicycle

14:59 and you just think about it in these terms, you can get to the place where you

15:04 understand it just using this simple linear momentum model.

15:08 I recognize that I probably said a lot of things wrong,

15:11 but this is just a mental tool that allows

15:14 me to understand what's going on, and I love it.

15:17 I think it's really, really cool.

15:19 So what if we did it one more time and you got to guess?

15:21 Do you want to do that?

15:22 Okay, so let me spin it the other way.

15:25 I'll spin it the other way and you guess where it's going to go.

15:31 It's rotating.

15:35 Maybe not as fast as I want it to.

15:37 But now, if it's rotating this direction and I put the air down right here,

15:42 what's going to happen?

15:49 My hope is that you now understand this and you

15:53 enjoy it because I think it's really neat.

15:56 It took me a while to understand

15:59 exactly what was going on with gyroscopic procession.

16:02 I just think of it as a rotating mass that's being hit.

16:08 I think of it as just generally a billiard ball that's rotating.

16:15 I guess I have to balance it.

16:16 I think of it as a billiard ball that's rotating in this direction.

16:21 Then if I hit it as it's rotating, it has to go down.

16:24 It goes down like that, which tilts the thing like that.

16:28 That's how I think of it.

16:30 All right.

16:30 Well, there's an imperfect physics analogy that I'm

16:33 sure the internet is going to love.

16:34 Now what I want to do is I want to show you a really cool thing.

16:38 Every year on Smarter Every Day,

16:40 I create stickers for people that support Smarter Every Day on Patreon.

16:44 And it's a gimmick.

16:45 It's totally a gimmick, and everybody's in on the gimmick.

16:47 My goal here is to make intelligent,

16:49 respectful content that's just genuine and fun.

16:51 And people that support on Patreon allow me to be free from the algorithm.

16:55 The idea is I want to thank you for sticking with me.

17:00 It's a dad joke.

17:01 But the cool thing is these stickers only happen once.

17:03 If you're either in that sticker team or you're not,

17:06 and I want to show you this year's sticker team.

17:08 So on Patreon, patreon.com/smartereveryday If you are

17:13 a patron by the end of January, We're going to cut it off then.

17:16 I'm literally going to mail you these stickers,

17:18 and you can do whatever you want with them.

17:19 They're really fun.

17:20 Okay, so I asked the patrons, What do you want as a sticker?

17:23 And the overwhelming response were two things.

17:26 The first one was the smarter scrubber.

17:29 This year's one of the stickers here is the smarter scrubber.

17:34 It says, I support local manufacturing because we wanted

17:37 it to apply to people who don't live in America.

17:40 The purpose of that video earlier this year was about made in America.

17:44 But I think no matter where you live, you should support local manufacturing.

17:48 So the smarter scrubber, I support local manufacturing.

17:52 I love this one.

17:52 We went through a lot of iterations.

17:54 The smarter scrubber, if you don't know, it's a chainmail grill scrubber.

17:58 The purpose of that is so if you're cleaning your grill,

18:01 you won't get those wire bristles on your grill, which can be a medical issue.

18:04 But the smarter scrubber sticker is beautiful, and I'm excited about that.

18:08 The second sticker, we.

18:11 So we did a nuclear power series this year.

18:15 We started the nuclear power series.

18:18 One of the first things we did was we visited EBR1,

18:22 and we talked about a fast reactor, and it uses fast neutrons.

18:27 We created this little character called the Fast Neutron.

18:29 Weeeeeee!

18:30 And he shoots across the screen.

18:32 And so I think this one's really, really fun.

18:35 So you can get your own fast neutron

18:37 to put anywhere that you feel needs neutron radiation.

18:40 And that's a sticker.

18:41 You can do whatever you want with it.

18:43 It's made to look like felt.

18:44 I love it.

18:44 And then this is the Big Daddy sticker.

18:46 This is the big one.

18:48 All right, here we go.

18:49 The smarter everyday nuclear power team sticker.

18:53 So this is only going to happen once.

18:56 I love it.

18:56 It looks like lithium.

18:58 I got it.

18:58 It's the Bohr atom of the model.

19:00 Some people don't like the Bohr model of the atom.

19:04 I think I said that wrong, but I love it.

19:06 I think it's great.

19:07 Lithium is very important for fusion power, and so that's what we went with.

19:13 So if you would like to be a part of the Smarter Every Day nuclear power team,

19:16 this is your one shot to join.

19:19 If you're not a Patreon member by the end of this month, January, it's over.

19:24 You can't do it.

19:25 But if you are a member,

19:26 we're going to mail it to you, which I think is awesome.

19:28 So these are the three stickers.

19:30 So we've got the smarter scrubber, I support local manufacturing.

19:33 Really cool holographic rainbow-looking thing.

19:36 Then we've got Weeeeee!

19:38 Fast neutron, and then we've got the Smarter Every Day nuclear power team.

19:42 All right, that's it.

19:43 Thank you for watching this video.

19:45 I hope you enjoyed it.

19:46 This was just a thing that I wanted to understand better.

19:49 What better way to do it than to make a goofy contraption?

19:53 I mean, look at this.

19:55 It's wild.

19:57 And it took a really long time to figure all this out.

20:00 So I hope you enjoyed it.

20:01 That's it.

20:01 I'm Destin.

20:02 You're getting Smarter Every Day.

20:03 Feel free to subscribe if you're into that sort of thing.

20:06 If not, no big deal.

20:07 Have a good one.

20:08 Bye.