7 Myths About Movement


You move everyday, and I’m not just talking
about exercise or your daily commute. Every atom in your body is vibrating, and
you’re on a planet that’s speeding around the Sun, while the universe is rapidly expanding. And for all the moving we do… we don’t
always know how things get from Point A to Point B. So we’re gonna debunk seven common misconceptions
about moving things, and explain what’s really physically going on. If you’re on one of those spinny theme park
rides where the floor drops out, or take a really sharp turn in a car, it might feel
like you’re being pushed against a wall. Lots of people call this centrifugal force. But the truth is… there is no centrifugal
force trying to push you outward. Like, let’s say you’re riding in a car
down a long, straight road, which means both your body and the car are moving forward pretty
fast in one direction. And, all of a sudden, the car turns left. Because you’re not a part of the car, your
body still tends to go straight even though the car is turning, and this tendency is called
inertia. So when the car turns, you basically end up
crashing into the side of the car, so you’re forced to change directions and make the turn
with it. It feels like there’s some kinda force trying
to push you outwards, but really, you were already travelling in the outwards-direction
and the wall is just trying to keep you in. Even though bikes have been around since the
early 1800s, there are still misconceptions going around about how bikes work. We all know if you hold a bike still, and
then let go, it just falls over. But if a bike is moving, it can glide along
gracefully and accident-free, even if there’s no human on board. That leads people to think that a bike stays
upright simply because it’s moving forward fast enough… but it’s a little more complicated
than that. Turns out, there are lots of physical factors
that work together to help bikes stay upright. And one important thing is the position and
mass of the front wheel and handlebars. The front wheel of a bike is slightly in front
of the handlebars, so that the turning axis is at an angle. Plus, the weight of the front wheel and handlebars
is generally towards the front of the bike, concentrated slightly in front of this turning
axis. These things mean if the bike starts to fall
to the left, for example, the wheel will automatically turn to the left. So the bike can basically correct itself and
stay balanced, as long as it has enough speed so that the wheel can roll and move back under
the bike’s center of mass. This is also why people can steer bikes without
their hands: you just lean your body in one direction, and the wheel will naturally turn
in the same direction. But there’s other factors that help conventional
bikes steer, such as the gyroscopic effect, which happens when you have a spinning object,
like a wheel. When a force pushes down and left on a spinning
wheel, the push will also cause torque, the ability to make something rotate, making the
wheel turn left. With all these different features playing
small parts, bikes are really just designed to keep their wheels beneath their riders. For planes to fly, they need to create a lift
force which is at least as strong as the force of gravity. And lift force is created when there’s a
pressure difference between the bottom and the top of the plane, basically, we want more
air molecules hitting the bottom of the plane than the top. Now the question is: what makes this pressure
difference? There’s a myth going around that’s become
so popular, it even got its own name: the equal-transit fallacy. The idea is that when air is sliced by an
airplane wing, some air travels above the wing and some air travels below the wing. Now because the top of the wing of most planes
is designed to be longer than the bottom, the air has to travel a farther distance before
the air reunites on the other end. Because the air has to travel farther, it
goes faster. And something called Bernoulli’s principle shows us that faster moving air
means less exerted pressure. So, the top will have a lower air pressure
than the bottom, and the plane will fly. So simple! But… not quite. That explanation
doesn’t actually add up. It’s true that the air on top of the wings
moves faster than the air underneath, but this normally doesn’t create enough pressure
difference to lift a whole plane. Really, it’s because of the fast-moving
air above the airplane wings plus the fact that wings are typically tilted slightly upwards
and curved. This causes much more air to hit the bottom
of the wing and prevents air from hitting the top of the wing, pushing the plane upwards. In the early 20th century, there was a misconception
going around that bumblebees shouldn’t be capable of flight. Now obviously we know they are capable of
flight because… well… they fly. But based on calculations using aerodynamic
theories from the 1930s, it seemed impossible because their wings were too small to create
enough lift. But the missing key was how the bees actually
used their wings. Bees don’t actually flap their wings up
and down, they’re moving their wings back and forth, while also rotating them. Basically, they’re trying to create a pressure
difference so that there’s lift. But instead of working like plane wings to
force air downward, they swirl the air and make small vortices, which looks like a mini-hurricane
with low pressure in the middle. The wings move so that a vortex forms and
creates a low pressure region above their wings, and the pressure difference creates
enough lift for the bee to fly! So bees used to confuse the world’s physicists,
but now we have a much better understanding of how fluid dynamics work to keep their chubby
bodies in the air. When you see astronauts up in space, they
appear weightless and you might think that they’re just floating around gravity-free. But actually, gravity is everywhere, and it
can be pretty strong in space! Gravity is a force that pulls any two objects
with mass in the universe towards each other. Even you and your friend standing next to
you are being slightly pulled together by gravity. And the more mass you have, the stronger your
gravitational field. So the Earth has plenty of mass, and the force
of gravity really does pull astronauts towards the Earth as they orbit it, but they don’t
crash into the ground. The key is that astronauts are also moving
so fast sideways that they’re falling and missing the ground. The reason they don’t even notice the gravity
is because everything else is also falling around them too, like the floor, their food
and their fellow astronaut friends. So if everything is falling, it’s almost
as if nothing is. Except for maybe a few people falling for
this misconception. When you turn on a lightbulb, you see the
light turn on almost instantaneously. And electricity is the flow of electrons in
a wire. So you might think that electrons are moving
super, super fast, and travel all the way from the battery to the lightbulb in a matter
of milliseconds, right? Well no. The electrons are actually moving
super slow down a wire, like, slower than a minute hand moves on a clock. See, the wire is already filled with electrons. And because the wire is conductive, some of
these electrons are free to travel around When the light switch is off, this electron
movement is pretty random, with no particular goal. When the light switch is off, this electron
movement is pretty random, with no particular goal. But when you turn the light switch on, you
complete a full circuit between the positive and negative terminals of a battery. Now, we know that opposite charges attract
each other, and similar charges repel. And because electrons are negatively charged,
they’ll favor moving towards the positive terminal, which will be either towards or
away from the lightbulb. We call that small movement the electron drift
velocity. However, there’s also something called a
signal velocity, which tells us how long it takes for the lightbulb to feel the effects
of this force, and light up. You can imagine signal velocity kind of like
a long line of people kind of squished together. If the person at the back pushes forward a
little bit, it’ll cause a domino effect where all the people in the line move slightly
forward. Nobody moved very fast, or very far, but the
signal travelled through the line very quickly. In a typical cable, the signal moves at about
two-thirds the speed of light. So almost instantaneously, the electrons in
the light bulb start moving slightly, causing the filament to glow! If a penny fell from a really tall skyscraper,
like the Burj Khalifa in Dubai, would it fall fast enough seriously hurt someone walking
on the street? Luckily, the answer is no. The big misconception comes from thinking
that objects keep accelerating when they fall, and they do for a little while, but not forever! As the penny gets faster and faster, it starts
to experience more and more drag, basically air molecules hitting the penny and slowing it down. Pennies don’t have a very aerodynamic shape, so they experience a lot of this air resistance. Also pennies are pretty light, which means it doesn’t take much air resistance to counteract the force of gravity. When the air resistance is as strong as gravity,
the penny won’t fall any faster no matter how far it falls, it’ll reach its maximum
speed, called its terminal velocity. In fact, different researchers have experimented
with throwing pennies off of skyscrapers, and found that pennies reach their terminal
velocity after about 15 meters. So whether it’s a 5-story building, or a
50-story building, the penny will be going at the same speed, which depends on the conditions
outside, but can be around 50 kilometers per hour. For the poor person below, a falling penny
would just feel kinda like a flick to the forehead. Thanks for watching this episode of SciShow,
brought to you by our patrons on Patreon. If you want to help support this show, just
go to patreon.com/scishow. And don’t forget to go to youtube.com/scishow and subscribe!

100 thoughts on “7 Myths About Movement”

  1. Gravitation force is no more a force than centrifugal force is a force, they're both forces conceived to make classical motion equations work out.

  2. In physics we were taught that rotational motion – let's say a ball on a string spinning around an axis – is a special type of accelerated motion and so the inertial force is called centrifugal force and is counteracted by centripetal force, which is the force necessary to prevent it from breaking out of this circular path.

  3. "Lots of people call this sentri-fue-jull force". No, they don't. They call it "sentri-figull force

  4. Playing with paper airplanes can show this. I have made paper airplanes of the long and narrow sort and torn ailerons (?) on the back edge, one on each wing. If they were up, the plane flew up (often stalling and dropping). If I turned them down, the air that hit them would push the ailerons up and the nose would go down and crash. Quickly. 😫

    So yes, air pushing against upward – turned ailerons and winglets do control the nose directly.

    What was fun was to reverse one winglet from another and get a good barrel roll out of it! 😊
    However, physics and civil engineering worked against me if I pushed my left winglet up and my right winglet down.

    The force of a twist (torque) goes one direction only, and you can find it by putting your right hand in a fist with your thumb out. Your fingers go in the direction of the twist, and thus the thumb points in the direction of the twist.

    So to make the force go forward, I needed to tip my right winglet down to force the nose down, then tip my left winglet up to force the nose up. Curl your fingers from the top of the plane to the right to the dropping side (right), and under. Follow the tilting force of the left side — it's going up—and you have the direction of the twist. Where is the force going? Follow the thumb: it points to the nose of the plane.

    Jet pilots will do a barrel roll by tilting down on their starboard side to do just that, to take advantage of the forward torque.

    When I made the winglets the other way — right side up and left side down, then the right side would go up and the left side down. Following the twist, my thumb would point backwards, and the backward force would cancel out any forward force I would launch it with

  5. The visual of the bee wing and description seems similar to the sculling technique we used in synchronized swimming for staying vertical while upside down

  6. This episode really is truly painful. You might get away with either the centrifugal force thing or the no ';force' of gravity in space thing, but you can't call both wrong. Both are artefacts of how we choose frames of reference, so there is no way that one can be called a force and the other not. Centrifugal force might be a misnomer, but is obviously a real effect.
    The flight section is also wrong. The differing speeds of the fluids moving above and below the wing are how they work*, and the fallacy is about why a difference in velocities exists. The fallacy is assuming that the top air has to meet the same bottom air, so travels faster to cover the longer distance. The air doesn't have to meet the same 'partner' though, so some other reason must exist for the differing speeds.

    *The energy for accelerating the air above the wing has to come from somewhere, and it comes from air pressure. Once passed the wing the air slows again and repressurises, making the whole process occur without the aircraft having to put significant energy in. This is why it is efficient at generating lift.

  7. Crap. This sounded interesting, but I just can't watch her. It's ironic that she is doing a show on movement. LOL

  8. About the bicycle, it's called counter-steering. If you ride long enough you will eventually learn to do it naturally. Another two wheeled vehicle that benefits greatly from the countersteer is motorcycles. Same concept. Also, I thought it was mostly the gyroscopic action of the wheels that maintains balance and provides the countersteer?

  9. The Penny off a tall building one… that I knew. Of course, the story would change if it was a carefully-dropped sewing needle made of tungsten…

  10. Could not listen to the mindless rising inflection – a statement should not sound like a question!!!!!! (Does she know that there's something hanging from her nose? It looks yellow and shiny.)

  11. Well Scishow, you started out with a lie. We all know that planes fly because we believe they will.
    What lie are you going to try next? Evolution? Or are you going to and sell me the b.s. that the world is older than 6k years old?

  12. 7:10 It isn’t signal velocity. If the guy in the back pushes then they guy in front of him will turn around and give him a good one

  13. So the sun the galaxy and the universe are falling? Also inter galactic objects such a rogue planets are falling?
    Everything is falling in every direction? Really? Or the real reason is "I don't Know" you don't know, they don't know.

  14. Want to chime in:
    I don't like the metal in her face either.
    But what does that have to do with anything? Does it in ANY WAY invalidate the content of her video?

  15. "Even you and your friend standing next to you are being slightly pulled together by gravity"

    This is an informative science video, honey. There is no need to bring "friends" into this.

  16. People not understanding the difference between centrifugal "force" and centripetal force in the comments, thinking centrifugal "force" is an actual force. I'll just carry on.

  17. You illustrate a DC circuit for a light switch where, at least in North America, it's AC and the electrons are only moving back and forth;
    Regardless, this is a cool video

  18. I've never heard of any of these misconceptions before. Kind of wish videos that bust myths didn't have to introduce you to them 30 seconds before busting them.

  19. WRONG! Mass does not equal gravity. The sun now has the gravity of 1 sun, if it was shrunken down to be Earth sized- the gravity increases even though the mass is the same. It's not the mass, it's how much mass is in a single space. More mass, same density = stronger gravity. Same mass, higher density = higher gravity. More mass, decreasing volume = blackhole a.k.a inescapable gravity. Gravity is NOT (entirely) based off mass. Gravity is more determined by how much mass is in a single volume. The more mass in the volume, the higher the gravity. More mass but lew density or larger volume doesn't always equal stronger gravity. In fact Earth has higher gravity than Saturn, the (roughky) third strongest gravity of all planets in the solar system. Saturn is over 90 times Earth's mass but is the least dense planet in the solar system, less dense than water. Earth is the 5th most massive (most massive terrestrial planet) and the most dense planet in the solar system, and one of the most dense objects in the solar system period- giving it higher gravity. Higher SURFACE GRAVITY anyway. In other words the strength of gravity at the surface (on the atmosphere for gas giants) Now, Saturn's gravitational grip at a distance is greater than Earths. Gravity is complicated.

  20. I'm sorry, am I the only one who finds her nose jewelry making it difficult to take her seriously and pay attention to what is being said? I love math and physics, but I also know in the business world, professional attire really makes a difference. Otherwise she has enough passion and knowledge to explain these subjects quite well. Anywho, have a nice day.

  21. OMG. Centrifugal force is the name we give to force that occurs under curvilinear motion. Because it's not one of the 4 known fundamental forces doesn't mean it doesn't exist. Does an impulse not exist because it's not one of the 4 fundamental forces?

    Thumbs down.

  22. If outer space is a vacuum ( no particles/ no mass) and gravity works on an inverse square relationship how does gravity or Relativity work in deep space i.e the expansion of the universe? Think people Science lies

  23. I remeber an episode of family guy where peter was so fat the brian tossed the tv at him and it just ended up floating in a circle around him, making a poing why peter should lose some weight.

  24. So if I drop a 50 Cal. bullet from Burj khalifa it would kill some one, right?
    √(2×9.82×800)=125.3475169279
    125.3475169279×3.6= 451.2510609404 km/h
    (that's 282.0319130878 mph for you folks from across the seas)
    And the 50 Cal. Is designed to go around Mach 2 soooooo yeah, argument over, I won

  25. … centrifugal force? It's called Centrifical force you absolute ignorant pile of stage presenter. Whoever's doing your research for you is very clearly not a native English speaker. The word is centrifical force. Just like the medical device that spins little vials around in a laboratory like to separate blood cells and plasma from a blood sample is called a centrifuge. Centrifical force exist as a term to describe the special form of inertia that happens when the object is rotating full 360 degrees over the same distance in roughly the same position. The outward force acting on the object being spun around ask slightly differently than regular inertia.

    Please get someone on your editing staff as a final proofreader who is educated in the United States long enough ago that Latin was still a required language in high school. #SeniorsNeedWorkTo Cuz clearly whoever your Outsourcing this work to is obviously not familiar with formal academic English. They're most likely transliterator , not an actual translator who can put terms and ideas into cultural context and use the time. Appropriate word. In all my years in University I have never heard any Professor use the word centrifugal…

  26. When I first heard that one about Bees I was like…don't be stupid, they can fly so you just don't understand how they fly.

  27. Wow, SciShow USED to be good about checking sources, due diligence, and getting correct info out there with an entertaining delivery. This video, along with one from SciShow Psych, have so many errors and so much misinformation that it's laughable! I am glad an aerospace engineer chimed in about the MASSIVE misconception of how airplane wings generate lift. The idea that the air colliding with the underside of the wing at a high angle of attack is what pushes it upward, is hilarious! If that were the truth, planes would fall out of the sky any time they pitched down to descend! Not to mention that when you have high angle of attack as she is saying GENERATES the majority of the lift, the truth is you will be close to the the phenomenon known as aerodynamic stall, which is a fancy term meaning loss of ALL lift!

    The whole centrifugal force thing was also severely mistaken, else how would you explain how centrifuges work, or even the force you feel on a merry-go-round? Ditto for the zero gravity thing. Geostationary orbit is closer to what she explained about the falling and missing the ground thing. Geostationary orbit is achieved in micro-gravity, not zero gravity. There definitely is such a thing as zero G, it just happens further out from Earth, and away from anything else's gravitational pull. If there is a miniscule amount of gravitational pull from ANY object, as she says, I argue that it is so slight as to be considered negligible, hence zero. I guess nobody told NASA they don't need to have their astronauts tether their tools to their suits, as their gravitational pull should be suffice to keep their tools from floating away, huh?

    SciShow, if this is the level of quality we can now expect from you, then you might as well stop making videos. Either that, or change the name of the channel from SciShow, to SciFarce.

  28. A penny isn't "slowed down" by air resistance. Its acceleration dwindles to zero and consequently, the velocity becomes constant. (Persnickety minor detail).

  29. Does terminal volatility work with throwing because I have had a penny thrown at me and it didn’t feel like a flick

  30. I keep seeing the claim that a bike will keep going with nobody riding. I call BS. I've sent a bike off by itself many times and it ALWAYS falls down after just a few feet. ALWAYS.

  31. Good info except the gravity BS. I remember science experiments in 5th grade dropping objects of different mass from the same roof at the same time & they travels at the same velocity. If your flawed theory of gravity so many NASA clowns cling to were true, than these objects would be pulled at varying rates by gravity. Neil Degrasse Tyson even admitted on video that gravity is a theory. If science is unable to recreate it in a controlled experiment, it's theory, not a law of physics. Density is real. Gravity is a desperate attempt to prove other fallacies like traveling through the van Allen radiation belt in a "magic alloy" tin can & the technology of a Texas Instrument Calculator which NASA has publicly stated that we "lost" that technology 50 years ago lol. What a joke.

  32. Mythbusters busted the penny myth all the way back to their first season I believe. A penny will hurt alot more than a flick but still won't do any more than a cut and a very bad migraine.

  33. I think a penny falling would hurt more than stated in the video. I would
    think that penny falling from that height would give you a good shot. It
    may even cut you, or leave a bump. The heavier the object dropped, the more
    damage it would do — you would think ? Common sense. Just like a big
    hail ball hitting you in the head, would seriously hurt you, a lot more than
    a drop of rain would. Matter of weight.

  34. I may get some hate for this, but I'm usually not very fond of her presentation skills… I still enjoy the videos, but something about her presentation feels off…

    In this video, I'm not getting that same vibe. But I can't put my finger on what's different

  35. U are hot I love the videos you post I shouldn't watch on a Saturday night when iv had a drink. But don't pay a tension to me i still find you hot even when iv not had a drink x you are amazing

  36. A penny hitting you at 50 might not kill you but sure seems like it would be more than a flick of a finger on a pain scale

  37. I have seen pine needles fall from a tall pine tree w enough force to puncture plant leaves in my garden leaving the needle (butt end first not the needle end) half way through the leaf or in a cactus 1/8 of an inch deep

  38. The poor girl. She falls into her dad's fishing tackle box and you force her to make the video before going to the ER? Horrible.

  39. I'm guessing you are a cat person, very intelligent, very beautiful, but a bit of a weird mess lol. Keep up the great content guy's

  40. 6:50 if anyone's confused as most even modern diagrams show flow from positive to negative.. Do not worry, you are not alone. here's a video explaining that https://www.youtube.com/watch?v=IzY0wuxt1R8

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