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Today we'll be discussing inertia and Newton's 1st law!
Hit me up with your creative interpretations to this class on Insta, Twitter, FB, or TikTok to win some Bose 700s. Alternatively you could tell your friends about our class here together. 8 winners. Maybe do one of the demos or a new one or make a video teaching your friends a principle from the class!

I stream classes every Wednesday at 1pm!
Check out Dianna's channel where she did 20 experiments around her house in 5 minutes!
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Welcome back besides class, I'm your host Mark Rover, this is live, and it's good to be here today will be answer the question: how do astronauts weigh themselves in space in space is implied there? Because if you know, if you're rigging in zero-gravity your waitlist a scale will just float right by you right, so what happens? If you step on it, it's gon na read zero. So how do they know if they're gaining weight from all that astronaut ice cream, we're gon na figure it out we'll give ourselves three clues as usual, we're gon na use as few equations as possible, so you're gon na want to stick around to the end, because I'm going to talk about, I said I would do these for two weeks and then we'd see how it's going. I'm gon na tell you what we're gon na be doing moving forward and kind of how it's going well, let's just get right into it. Here we go clue, number one objects are lazy, Newton's, first law states, objects are lazy.

All right. This hammer is just chillin here and it's not moving. It's not gon na move until unless something comes and pushes it and makes it move and if it is moving, it's just gon na keep moving until some other force comes and stops it all right. So it's kind of like you're on your couch and your mom's like hey, you need to let the dog out and you're like, but I'm already on the couch, I'm not moving.

I don't want to move right or maybe you're walking out the door now you're moving and your mom says hey. Could you come back here, real, quick? You need to let the dog out and you're like ah, but I'm already moving right. I don't want to turn around, so we have on this table right here. Some objects that are currently not moving.

We also have a tablecloth underneath these objects. So what do you think would happen if I were to pull this out really quickly? Well, these objects. If Newton, if Newton knew what the heck he's talking about are gon na want to stay still, okay, here we go one two and don't try this at home. By the way.

This is for trained physics. Professionals, only all right count me down. One two actually do try it at home, but you should like check with your parents. First, you should practice with things that aren't your wife's, really nice glasses in place that she doesn't know you have alright.

Here we go. I only rehearse this once this may not work here we go physics, one two, three yeah. I could count that as a win all right here we go. We're live we're switching out the set the objects.

You'll notice did not move okay back in here now. We've got another example. I've got this ball in this wagon. The ball is not moving.

What happens if I move the wagon this way. Well, objects are lazy. Is it going to come with it and just stay right there? Is it going to move backwards or we'll stay right where it's at let's test it out, one two three whoa, probably move forward just a little bit because of friction, but for the most part it stays right where it's at okay. So that's two examples of this concept of Newton's: first law, where the things were stationary and they just wanted to continue to be stationary now, let's do two examples where they're moving I'm gon na put this ball at the back of the cart.

Now I'm gon na move it and then stop. The cart should have an intuition on what's gon na happen right, the ball keeps moving. It's like yo, I'm moving. I just want to keep moving.

That's what I'm doing all right here is another example that you know this stuff already you're, just as smart Newton as Newton, you got this ketchup bottle if you need to get the ketchup out, what do you do? Well, you do this. Why do you do this? Because you're, like hey ketchup in bottle, move together the same speed, but I'm gon na I'm gon na arrest the motion of the bottle over a very short period of time that ketchup is going to keep moving and move to the bottom right. That's Newton's, first law! So this is why, if you're in a car and you're going 50 mile, the cars going 50 miles an hour. So are you if you hit a brick wall, there's a moment in time where the car is stopped and you're still going 50 miles an hour? This is why seatbelt and airbags are important when we send stuff to Mars.

We put it in this spaceship. We get it out of our atmosphere. We don't actually fire a rocket the whole way there for nine months, you just fire it right. At the beginning, you fire it and then you glide to Mars at 25,000 miles per hour five times faster than a bullet.

That's like a hundred and fifty football fields, a second right. You glide real fast because once you're moving Newton's first law, once you're moving you're gon na keep moving until some four stops you from moving, we even have little motors on there. We call them like mouse. Fart motors, you just need a little poof, nothing much just a little poof.

If you need a course correct right, cuz over such a long distance, even if you move an inch over, you know a thousand miles that adds up and could mean the difference between missing Mars and actually landing. Okay. Here we go clue number two we're getting close to answering this question: good, throw inertia all right. What is inertia mean? Inertia is a body's ability to resist motion right so think of like a huge semi truck versus this wagon, which resists motion easier, which is easier to push to get going.

Obviously, the wagon right, which once it's moving if a big trucks coming out and you have to stop it, which is easier to stop well, obviously, this wagon, you can have this hammer yeah versus this big weight right. If one of these is coming at your head, which one did you rather be well, this light hammer because you could just deflect it out of the way right, this big weight resists being moved better, so it has more inertia. So did you know that ships big ships, cruise ships, cargo ships, when they're coming into port, they turn off their motors they're like 25 kilometers or 15 miles out from the port, because they just have that much inertia to slowly come to speed and to come into Port, so heavier things have more inertia and guess what you knew this too, you are basically Isaac Newton. If I handed you this piece of duct tape and this spool of copper wire, I said: put out your hands.

Okay, do this with me put out your hands? Imagine you've got these things and I said which one weighs more. What do you do? I guarantee you what you do intuitively? Is you move them up and down right? You go okay, okay, okay, all right! You don't just sit them still right. The heavier one will resist changes more and so you're determining which is heavier by trying to change its motion in time. The one that resists that more to your muscles is the heavier one.

So if you were gon na crash into me, if I was gon na play football, I'm a soccer player, I just don't have the body for a football player. But if I did play football, I would take one of these 25 pound weights, sneak it under my pads. Why that would give me more inertia, more ability to resist changes in motion. So if you ran up and crashed into me aside from the fact that this would be hard, I feel it less right if a football player hits a brick wall at pre-qual and going anywhere so the more mass you have.

The more yours is that motion now, keep that in mind. We're gon na do something here, let's switch cameras. I've got a bunch of nails here now, lest you say, these are like plastic, fake nails. This is just an apple little Isaac Newton action boom.

We just impaled this Apple, all right, so I'm gon na do something crazy. Want you to see if you could spot the cheat, I'm gon na do something that seems more crazy, but in reality it's actually making it easier on me. Okay, I'm gon na lay down here, I'm gon na get some help or my trusty assistants. Okay, Thank You.

Eli. These nails are now on my chest and we're gon na put a big fat heavy cinderblock on there, and now my friend Alex when I count to three is gon na shatter that cinder block okay, this is live. Anything can happen, you ready Alex. If this hurts your fire here, we go one: two, three yeah okay.

Now, let's go to the wide camera and tell me if you were able to catch the cheat all right. What did I put on that right? At the end, I put this big heavy block right. Why did I do that? Well, the truth is, it would have hurt a lot more if Alex would have hit me with that sledgehammer without this brick. Why? Well, this brick has mass it's heavy.

It has a lot of inertia right so when that sledgehammer hit it, I didn't even feel that sledgehammer hit for a little bit, because this brick was so heavy. The sledgehammer is trying to move this that it's like uh-uh. I ain't moving right so while it might have seemed more extreme, it actually saved me from like feeling more force right. So here's a question is this: cinderblock really is heavy in space.

Would it be heavy well stuff floats in space right, there's no gravity. So, what's up with that, that leads us to our last clue clue: number three: the concept of mass versus weight, all right, so mass is just a measure of how much stuff is in a thing, all right. How many atoms are in there? Basically, so weight is how the object interacts with Earth's gravitational field right so basically, on Mars gravity is one-third. What it is here on earth.

You could dunk a basketball on Mars on the moon, it's 1/6, so you could basically hold this pretty easy on Mars. On the moon, you could really hold it easy, but there's one thing that wouldn't change right. If I were to hand this to you on Mars or the moon or even on the International Space Station, I said how much it weighs guess what you would do. You do the same thing you here on earth and you move it back and forth that doesn't change whether you're in space or weather here on earth yeah, it's gon na be heavier due to gravity, but the mass.

The ability to resist that motion is the same. All right, so you thinking ahead, so you can't use a scale on the space station to get your weight, but there is a way to see how much mass something has or by. Conversely, if you want to convert it, multiplied by its gravity and know the weight and here's a clue, maybe you're getting close to figuring out our answer all right. I've got this paint bucket and a spring here and you'll see, look how frequently it goes up and down right.

Okay, now I'm gon na change it with something it doesn't weigh quite as much. I want you to compare the frequency, how frequently it goes up and down. So this goes up and down more frequently, it has a higher frequency. We call that the natural frequency - it's proportional square root of K over m fancy words K basically means how stiff your spring is and M is.

The mass is what you have hanging here, so the lighter the mass, the higher this natural frequency would be. Okay, you're getting it you're kind of honing in on what the answer is. Let me show you something right here, so this is one of those things at the playground right without anyone on it. This is how quickly it goes back and forth, and if I were to walk up and, of course, coronavirus proof it first of all safety first and then I got on it.

This is how it naturally wants to go back. That's lower-frequency, that's happening less frequently, and so that gives us an answer to we'll come back to the computer. This is actually on the space station, see if this looks familiar. An astronaut gets in some device check him out, so they know the stiffness of that spring and so, however, many times he goes back and forth that tozi his mast, here's another version, that's more similar to the one that I was going up and down here with So, the more frequently he goes, the less mass that person has the fewer atoms, the slower he goes back and forth the more mass okay there's another way you can do this using our good old F equals MA, which we talked about.

If you were to push. Let's say this is on ice. If you were to push with a known force, my arms, this would accelerate slower. Then say this lighter hammer right if you were to push same muscles, my arms same force, this is gon na accelerate faster, so another way they do.

This is with this an instrument like this depending they know the force of that arm and depending on how quickly they accelerate you can back out, you could solve for what the mass is. So that is how astronauts weigh themselves, they use inertia and they use our good old buddy Newton, and you knew a lot of this stuff too. So, hopefully, what you didn't know, though, that wireless transfer worked for my brain in two years, knowledge transfer complete. You can rewatch that if there are some parts that you missed all right, this has been really fun.

For me, I've really enjoyed doing these live classes. I want to keep doing them. I'm gon na commit to doing them for another month. However, I'm willing to do one a week because it is sort of hard with all this going on to do three week.

I'm doing this all for the first time and I want to keep making my normal videos and spend time with my family, like the coronavirus, is kind of an a bummer, but it has provided the opportunity just to hang out and spend more quality time together. So I don't want to miss that opportunity, so we're doing Wednesdays, 1:00 p.m. I'll do that at least for a month and then, once again we revisit. Hopefully you guys are having fun with this as much as I am.

So, let's look at some responses to the challenge. Video then I'll, give you the challenge for this week. This was amazing. Here we go.

This is a 100 paper clip machine. All right, you guys are so stinking creative. I think I don't want to pigeonhole you. I've decided and give you a specific challenge.

I want you to just blow my mind: teach some of these demonstrations to someone explain to the camera. What inertia this do. Some of these demos come up with your own demos. Just do something do something cool and and send it to me, and I want to see it both gave eight of those nice a 700 bed phones to people who either shared about this class on social media or send in some of those demos.

So keep up. The amazing work that's been so fun for me to see what you guys submit. Okay. So that's the challenge for this time.

We're gon na get to next wednesday's question and a quick QA, but first I got to have our music moment. This is something I was thinking about recently I get I've been getting a lot of responses and seeing a lot of there's a lot of girls watching this class and women, which i think is fantastic. I recently went to Dubai and it was like all the top science kids in the country and more than half of them were women which surprised me because you think like. But at least some of the you know, they're no less progressive.

As far as like women's rights and stuff - and I asked them what's up with that and they're like look Dubai, it's a small country, we need everyone's brains, we can't just say it's just the dudes like we need everyone's brains, and I thought that was really powerful. Some of the best engineers I've worked with at both NASA and Apple were women, and you might have noticed my first three shoutouts were some of my friends who are who are into science and engineering, who were women, the last one Diana she has a great can Of channel called physics, girls, she just did a bunch of a video where she did a bunch of experiments. You could do all around your house, it's fascinating. You should go check it out I'll, put a link in the description, but I want the girls out there to have good role models for what you could be.

The challenges we face today in the world and that we will face in the near future are too big to cast aside 50 % of the equal pay, equally capable brains because of antiquated social norms. So this is all hands on deck. If you're a girl - and you like science and engineering but you're like it's, only guys know that Mark Rover has your back all right. Future generations have your back.

They need you to trailblaze and to make it more normalized to see more women in science and engineering fields in the stem and steam fields. All right, so you guys need to be the Trailblazers so that we can tap into that brainpower, which a lot of times is better than us. Dudes anyways all right rant over here we go here is the challenge for next time or the question I should say for my buddy Bob, hey, I'm Bob from I like to make stuff. I was sitting here working on my r2d2 and a thought came to my mind, and I thought I should ask mark so mark what would happen if all the toilets in the world were flushed at the exact same time.

Okay, an intriguing question indeed, next time we're gon na talk a little bit about pressure. We're gon na go a little bit more into the bed and nail stuff and even up the danger level. So with that class is technically officially dismissed. I will stick around and ask a few minutes of questions and then I'll see you guys next Wednesday all right.

What was your job in position when you worked at NASA? I was a cognizant engineer, so I was in charge of like one chunk of the Rober of the rover, so that was for like six years or seven years and so yeah. I worked with a team of people and but at the end of the day, was my design in my hardware, and I worked a lot of smart people, thermal analysts and stress, analysts and machinists and everyone. You have a massive team of people who help you do something like that, but that's how they do it. They divide the Rover up into chunks and everyone gets a small chunk.

Mine was very small by the way. What was your best April Fool's joke? The the backup camera one is like a classic where you take like a Freddy Krueger picture, put it behind, like your parents, backup camera or your wife's. In my case, they put in Reverse. They see this big thing.

That's a classic just a classic, my poor wife. She just has the patience of Joe being married to me. Let's see, okay, here's the question now: would astronauts weigh less or more when they fart it's complicated? Certainly, their mass is less and technically mass is really what matters force equals. The force of gravity is mass times, so I I would say the answer to your question.

The fair one is that they actually do weigh less, but that gets into like a parent weight which I didn't get into the other day. There's it's its technical but let's say less alright, one more question: how can you weigh something in space? That's too big! Alright, let's take this, let's say: there's an asteroid going around and well there's a couple different ways: one you could look at like the gravitational force. Two bodies coming together there's a simple equation as the attraction, so you could look at how much it's attracted when it goes by earth. How much does it move right? That will tell you how much it bends in Earth's gravitational field will tell you how much it weighs another way you could technically like.

If you have a rocket thrusters with a known force, you kind of push on them right in the same way force equals mass times acceleration. You couldn't do a Big Spring, but if you had rocket thrusters and you pushed on that ever so slightly - you would see, especially in space, where there's no air resistance. Exactly how much you changed its motion due to its inertia and from that you could easily calculate what the mass is. All right.

You guys are the best. This is really fun. I'm gon na see you next Wednesday. We got some cool stuff, we'll find out what happens if everywhere in the world flushes their toilets all at once.

This is hardcore science. We're answering the important questions see on Wednesday.

16 thoughts on “Science class #5- how do astronauts weigh themselves?”
  1. Avataaar/Circle Created with python_avatars Nick Hanson says:

    What law is the ketchup if u hold it upside down and swing your arm in a circular motion doing the bottom half of a sphere and the ketchup moves toward the top?

  2. Avataaar/Circle Created with python_avatars Mahiyat Safiyullah says:

    Simple mass in kg is the same wherever you go so mass times gravitational field strength equals weight. P.S. the gfs of the Moon is 1.6 N Kg-¹.

  3. Avataaar/Circle Created with python_avatars TheRedDemon says:

    im watching this while doing homework. im 4 mins in and iv learned more so far then in all the homework iv been doing for a little over an hour.

  4. Avataaar/Circle Created with python_avatars 152 Srikar Yendluri says:

    "That brick wall ain't going any where"
    – Mark rober 2020

  5. Avataaar/Circle Created with python_avatars Shadow Phoenix YT says:

    "Which is easier to move? The wagon or the Semi-Truck?"

    Strong guy: Can't move a wagon without making it go flying: "The truck."

  6. Avataaar/Circle Created with python_avatars Nick Reyes says:

    Tomorrow's someone's birthday. Dropping a video would be a treat for us, even for the celebration..
    Love you Mark. Happy birthday in advance.

  7. Avataaar/Circle Created with python_avatars Eric R says:

    I had your "calculate the weight of an astronaut" question on a final physics exam in college (Carnegie Mellon). I gave your response by using springs and the formula. However, I only got 1/2 credit because I failed to talk about the effects of the spring on the spacecraft — i.e. the spacecraft will exert a force on the spring as the spring interacts with the spacecraft. So, the answer is more complex than just a simple formula!

  8. Avataaar/Circle Created with python_avatars Aziz Fenais says:

    Mark, from a fellow Engineer to another, you are a great representative and admire your work. I learned from many things so let me try to payback and teach you something… Dubai is a city in UAE not a country 😋

  9. Avataaar/Circle Created with python_avatars Nick E says:

    My experiment is going to be which bachery works better a lemon or potato by putting them in surcets and seeing which light will be brighter

  10. Avataaar/Circle Created with python_avatars Samuel Rogers says:

    Why not weigh them when doing routine thrusts, for maintaining orbit distance. Just use a very accurate scale and see how hard they are pushed into it by the acceleration. If you don't have gravity just make your own.

  11. Avataaar/Circle Created with python_avatars Apple I says:

    Me: Seeing Inertia

    Me 2 seconds later: Singing Bill Nye the science guy because they heard inertia is a property of matter in the song.

  12. Avataaar/Circle Created with python_avatars Nothing\ says:

    Funny I should come across this. I was just wondering this question myself earlier today. The best I could come up with was to spin the astronaut and measure how much energy it takes to spin them up to a certain amount of angular momentum. Then you could work out from the energy required and figure out the mass of the object, or person. Of course this is wildly impractical and inelegant. So I'm sure they've got something better.

    In retrospect, I'm sure doing the whole thing linearly instead of spinning the astronaut would work, as well. Get something to push them, then measure their speed and how much energy the device put into pushing them and you should get a good idea of how much mass you just moved.

  13. Avataaar/Circle Created with python_avatars Aze says:

    …. Um, inertia IS newton's first law. You're literally talking about the same thing.
    "Newton's first law states that every object will remain at rest or in uniform motion in a straight line unless compelled to change its state by the action of an external force. This is normally taken as the definition of inertia." – NASA
    1. a tendency to do nothing or to remain unchanged.
    2. (Physics) a property of matter by which it continues in its existing state of rest or uniform motion in a straight line, unless that state is changed by an external force."

  14. Avataaar/Circle Created with python_avatars gangstreG123 says:

    An educational video by a NASA-level engineer, in 2020, and we still have video interlacing. Also why does he sound like a guy about 3-4 drinks in at a party?

  15. Avataaar/Circle Created with python_avatars Michelle Holmes says:

    I think I got it I’m on clue 2. The astronaut will stand on something that pushes them to a scale that will sense the momentum

  16. Avataaar/Circle Created with python_avatars Mark Rober says:

    Hit me up with your creative interpretations to this class on Insta, Twitter, FB, or TikTok to win some Bose 700s. Alternatively you could tell your friends about our class here together. 8 winners. Maybe do one of the demos or a new one or make a video teaching your friends a principle from the class!

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