There just isn't a better teacher. Your school is very, very fortunate to have you.

As a first year physics teacher your videos are really helpful.

Thank you Bruce, I wish I had teachers like you when I was at school. A teacher passionate about their subject makes a world of difference

I m 26 lucky not to go to school anymore. Yet gotta get up early in the mornin to go to work,.. watching a whole bunch of your video's while i hated school i probably wouldnt have hated it So much with a teacher like you.

@YeanyScience

6 жыл бұрын

thanks Eagle_Eye

The bucket experiment was performed by my mom when I was 6! Now I'm almost 28 years old and I'm an aerospace engineering grad student!

@heyman6412

6 жыл бұрын

Giuseppe Pipia that's sweet

@deesabird

4 жыл бұрын

How did she teach you? What did she explain to you that kept you interested?

Dear Prof. Bruce. It's awesome how you demonstrate the newton's law. But more interesting is how funny can be as the experiment variations take place. Very nice. Thank you for sharing.

Great wholesome science on KZread. Thank you!

I would have loved to have you as a teacher. Kids learn so much more by visual demonstration and by doing than by text book assignments.

Uaaaa! You were so close to that door with that tray... I got the creeps!

Yeah..I remember doing the bucket experiment when I was young... Seeing this brought back old memories... Loved the way you took it to next level with balancing toy, water cup and the egg... Will have my kids try them for sure...

Very nice, that is teaching an old dog new tricks. I will use that for my students.

I have had teachers explain this to me before, but this is the first time I really feel I know what is happening! Thanks!

8:57 notice the LED (clock?) above the door. When the video is in slow-mo, the display is messed up. Also, LEDs and digital cameras produce odd reactions. I think it's due to frame rates. That be a cool topic for a video one day.

@sleepydog9968

6 жыл бұрын

kzread.info/dash/bejne/loKK1q-mfM_Un6g.html

@neurofiedyamato8763

3 жыл бұрын

It is indeed due to the "frame rate" that is causing this phenomenon. LED displays don't show all digits at once. It uses a clock to sequentially show each digit from the lowest significant digit(right most) to the most significant (left most). It uses a series of logic gates that determine which segments of the 7-segment display to turn on, then it changes to the next digit as the clock cycles really quickly. So in reality only one digit is ever lit at a time. However due to the speed at which it cycles through the digits, our brain thinks all of them are lit at the same time. This is known as persistence. Cameras have much shorter persistence and so don' get fooled like our brain does. Although rolling shutter would apply, it is not the main reason why the display is messed up. You can see the rolling shutter effect when sometimes a digit and a half is lit at the same time. As i said, only one digit is supposed to be lit at a time. The rolling shutter captured the first digit lit but as the shutter scans, it ends up scanning the second digit causing seemingly due digits to be on at the same time. The camera's shutter speed relative to the refresh rate of the LED display leads to the camera catching the LEDs turning on and off sequentially. This effect is exacerbated when slowing down the video because each frame is played longer thus slowing down the LED display even further, making it much more obvious. You can see this effect with propeller blades. There's a rather popular video where a helicopter's main rotor is not moving due to the rotation of the propeller matching exactly with the camera's shutter speed.

Thanks Bruce, I love your videos and I have a bunch of them saved to make with my children.

Another great video Bruce! Just wanted to thank you for inspiring people with these kind of videos/experiments. I had a teacher or two like you when I was in middle school and high school (coincidentally in southeast PA), and they were instrumental in inspiring my career path more than I knew at the time. Back then we were doing fun experiments to learn about physics, and now I have masters degree in Aerospace engineering and have been working at Johnson Space Center for almost 10 years. You are no doubt a catalyst to so many educational success stories like mine. Thanks again :)

Another great video Bruce. Thank you

Just did this with my science classes. Awesome. Thank you.

Bruce, you would make a good farmer.

Sus videos de fisica demostrativa son excelentes. Bendiciones profesor

Excelente profesor.

3:25 Mad skills. Awesome teacher!

The balancing blocks and balance toys are a very nice twist on this classic!

Great video!

Your videos are amazing.

Awesome video

wish i would of had a teacher like you 20 years ago

Really very nice sir

It's camera FX.. Just kidding =D, science never lie and Bruce is the best teacher!

Amazing!!!!

This is what anxiety is made of! Haha Great Video!

Keep in mind that the water in the cup _is_ moving slightly due to an unequal radial acceleration; the water closer to the center accelerates less than the water closer to the board. This means that during the apoapsis, the water is separating a bit if the centripetal acceleration is less than gravity . The water is also compressing during the periapsis, but this is a lot less noticeable since water doesn't compress very well. If you used a much longer tube of water, this effect should be a lot more apparent. That's actually a pretty good problem to solve. If you have a test tube that's (x) meters long full of water, how fast would you need to spin it (where the top of the testube is at the center of rotation) in order to keep at least half (0.5x) of the test tube filled with water? Well, we want an answer in radial velocity (w) since the velocity is dependent on where in the tube you are measuring. We need to calculate the centripetal acceleration (Ac) at radius (r) and see at what values of w that Ac is equal to gravity (g). Fc = mv^2/r, Ac = v*2/r w = v*2*pi/(2*pi*r), or w = v/r, also v = w*r Therefore, Ac = (w^2 * r^2)/r = r*w^2 Since we need to find when Ac = g, g = r * w^2 Therefore, w = sqrt(g/r). We want 0.5x of the tube to be greater than or equal to g, so r = 0.5x. w = sqrt(g/(0.5*x)) Notice a few things: -Stronger gravity means you have to spin faster. -The less water you need in the tube (r gets larger), the slower you spin. -In order to keep all of the water in the tube (r -> 0) you would need to spin infinitely fast.

@YeanyScience

6 жыл бұрын

One of the things I love about posting is how additional information is added. I never considered the differential in the distance from the center of rotation for the water column and how it would affect the centripetal force. I follow your solution and the moment I read through this, wondered of how could we explore this further. The 4 foot plastic tubes that are sold for light protectors might be suitable doing a bit more experimenting, but this will need to wait until summer. Thanks for the explanation.

Is that how you make scrambled eggs? Just kidding. Your videos are fantastic. Thank you from Alaska.

I would really like to see a camera on the tray and its view of the water and surroundings.

I wish you were my teacher

Cool video, I can't help but notice the water not rushing to your hand, If I recall correctly Only the item attached to the string are accelerating towards you hand anything else wants to fly away like when the ball was let go.

Awwsome

I must admit, I mildly panicked every time you swung it ;D

@HebaruSan

6 жыл бұрын

After a while I tried to convince myself it was a plastic beaker

@YeanyScience

6 жыл бұрын

I NEVER use glass, always plastic. I should have made that clear

In a vertical circle velocity is not constant...as when it falls down due to gravity it's velocity will increase but when it goes up due against gravity its velocity will decrease. Velocity in a circular motion remains constant during horizontal motion

@carultch

2 жыл бұрын

Velocity in circular motion cannot be constant. You are mixing up velocity with speed. Perhaps the speed could be constant, but the velocity has to change if direction changes.

@sunilpant6327

2 жыл бұрын

@@carultch Yes that was a typo error. It's speed what remains constant

Great video. My biggest itch is safety glasses - especially that you show the experiment can fail, wouldn't want a broken glass beaker flying at my head with no safety.

@YeanyScience

6 жыл бұрын

I should have mentioned, ALWAYS ALWAYS ALWAYS USE PLASTIC, I would never do this with glass. I've dropped one or two at the end but never had a cup fly off, still I wouldn't risk it

Bruce Yeany, you have the skills to use a sling(ancient projectile launcher)

Hey, Bruce. Did you notice the scanning refresh of the LED clock above your door? 8:56

He’s a madman

The balancing eagle was cool, but what about combining this with a drinking bird toy?

9:54 I see you have a concave mirror in the back of the classroom. Maybe you can make a Schlieren image with it!

@koosnaamloos4291

6 жыл бұрын

Veritasium made a video on how to do this

@YeanyScience

6 жыл бұрын

I haven't tried it but will take a look

What you said sounded corrected however the diagram at 5:48 is incorrect. The ball will continue in a straight line tangent to the curve however it will follow the path of the string.The diagram seems to show it jet off at a 90deg angle.

Why does nothing move during the wind up and cool down?

I'm wondering if I attach an accelerometer to the base of the plate, would it show no horizontal acceleration?

@kallewirsch2263

5 жыл бұрын

For the accelerometer, "down" would always be perpendicular into the plate. The magnitude it senses would increase but thats all. The accelerometer only senses the resultant force you get by adding the centrifugal acceleration to gravity in the form of a vector addition. But so does the plate. Thus for both of them, their local "down" points into the same direction. so now we are left with one question. When you talk about "horizontal acceleration", from which point of view are you talking? From the point of view of the accelerometer, no there is no horizontal component. For it, the force still acts in its own Z-direction (assuming we can take the plane of the plate as the X/Y plane). For an observer outside the situation is different. He sees, that the plate is tilted against the reference of eg the floor. He is able to decompose the force vector into avertical and a non zero horizontal component.

I understand that the string (centripetal force) keeps the board from going in a regular straight path, but I don't understand why it creates acceleration towards the center. Is it because the board (and contents) it isn't allow to go in the regular path so backwards acceleration is created towards the fixed point?

@kallewirsch2263

5 жыл бұрын

it is a consequence of Newtons 2nd law: F = m * a which tells us, whenever a force acts, there is acceleration (unless that force is counteracted by another force such that the sum of those 2 forces is 0) You can look at the whole situation in a different way also (which turns out to be equivalent) Every object remains moving in a straight line with some speed. We call that combination of direction and how fast an object is moving the "velocity". (speed is just distance gone with respect to time, velocity also considers the direction. Speed is called a "scalar" (just a number), while velocity is called a "vector" (number in which direction). Velocity thus includes speed but is more then that. (But this is just so in the english language which differentiates between speed and velocity. Other languages don't do that. E.g. in german we use the same word for both and in a physics context we always are talking about "Geschwindigkeit" and strictly mean velocity (the vector) unless the direction is not important. In order to change the velocity of an object, you need acceleration. But this includes the direction also! To make a rolling ball change the direction it is rolling, you need to have some acceleration sideways. There are no 2 different words for accelleration to differentiate the vector version (direction is important) to the scalar version (just the number matters). In a physics context, acceleration is always a vector. (direction plus magnitude). So when changing the velocity of a rolling ball, acceleration comes into play (since accelleration is the way to change velocity) but it depends an the direction the accelleration is applied to what happens. To calculate the effect is pretty simple: it is just the vector addition. If the accelleration is in the same direction as the ball is rolling, then the ball simply rolls faster, if the accelleration is perpendicular (not in line with the velocity), it changes the direction and/or the speed the ball is rolling, if the accelleration is opposing the current direction, the speed decreases (we call that breaking). So how do we get some accelleration? Newtons 2nd law tells us: F = m * a, or by turning things around: a = F / m Apply a force and you will get acceleration. How much? Well, if the force gets stronger you will have more accelleration, if the mass gets more you will have less accelleration (a bicycle has less mass then a car, so the same force accellerates a bike more then a car) Also: I am not sure if you have the same misconception I had when learning those things in my first physics class. The centripetal force is not exactly generated by the object swung. It is the force you have to bring up (e.g. with your arms and which gets transmitted through the string) in order to force the object into the circular path. The circling object creates the centrifugal force, but in order to have it circeling you have to create the centripetal force which exactely counteracts the centrifugal force. If the centripetal force goes away, by e.g. letting go the string, there is nothing forcing the object into the circular path any longer. No circular path also means no centrifugal force any longer and from there on the object just continues in a straight line. So from the point of the string: the centrifugal force created by the object is pointing outwards, the centripetal force created by the human or by a central post is pointing inwards. You might eg. want to watch a the sports discipline of "hammer throwing". You can clearly see, that the athlet is leaning backwards a lot. This creates the centrepetal force counteracting the centrifugal force in order to force the hammer into the circular path. lg-swm.de/wp-content/uploads/2016/09/Simon_Lang_Foto_Heike_Geigl_1-1024x580.jpg

I don't quite understand why you said that the water is accelerating towards your hand at 6:45. Do you mean to say that because the centripetal force is acting inwards, there is an opposing force (centrifugal force) due to Newton's 3rd Law that causes the water to be pushed back? Also, if one were to draw a free-body diagram, would it accurate to say that there are 2 forces acting on the object? The force tangent to the circular path (inertia) and the centripetal force?

@carultch

2 жыл бұрын

You have several misunderstandings aout this. The centrifugal force is not a real force. It is an apparent force due to being in an accelerating environment. Newton's third law isn't really part of the picture for why anything is happening in this situation. If you draw a free body diagram on this system, there is the force of gravity, and the force of tension. At the top of the circle, they both act downward. At the bottom of the circle, tension acts upward while gravity acts downward. They both add up to mass*acceleration, so acceleration is downward at the top of the circle. And greater than Earth's free fall acceleration, because the tension in the strings also contributes.

Sir in vertical circle it's not constant... Also in a horizontal circle it depends on tension if a string is tied to a object

@LasseGreiner

5 жыл бұрын

I do not get your objections. Please explain!

When the tray with the glass of water is swung in a vertical direction and at the 12 o'clock position, why doesn't the water spill out since the force of gravity and centripetal force are in the same direction downwards? What force keeps the water at the bottom of the glass since centripetal force is center seeking?

@carultch

2 жыл бұрын

At the 12 o'clock position, the acceleration of the system is downward, and greater than 1-g. The tension in the string plus the gravity both pull it downward, and add up to the mass*acceleration, which is directed downward. The apparent gravity in the reference frame of the tray is always directed in the opposite direction of the tension, which means that the water feels as if it is pulled outward, the tray feels as if it is pulled outward, and the glass feels as if it is pulled outward. So what force keeps the water in the glass? No force. It is the inertia of the water as it travels along a path that is changing direction. If you were to break the string, the tray would fly tangent to the circle.

It's a good presentation about centripetal force but at the top of the circular motion both the g and centripital forces are downwards. why didn't they fall ?

@carultch

2 жыл бұрын

They are falling. It's just that they overshoot their target, because they have sufficient tangential speed.

Hi sir....is velocity remains constant during vertical circle motion?

@YeanyScience

5 жыл бұрын

good question, velocity refers to both speed and a direction and in this case the direction is constantly changing but is the rate of rotation changing? I can't tell for sure, I went back and tried it and also watched the video. it feels like it could be, try spinning something yourself and I would be interested in seeing what you think.

You broke the youtube song rules. This song should only be played on cute dogs and pets videos!

👍⭐🥇

1st .love the video by the way

@YeanyScience

6 жыл бұрын

that was quick!

@oofboy-hz7um

6 жыл бұрын

Yea 😊😁😁😚❤

It would be great if you'd explain what the key difference is that causes it to fail. How can you figure out how fast you actually need to move it?

@carultch

2 жыл бұрын

Given a string of length r, you need to swing it at a speed at the top of the circle where v^2/r is greater than 9.8 m/sec^2, so that the acceleration at the top of the loop is greater than Earth's g-value.

Hey Bruce I'm not trying to be smart but how do you explain these forces that make water stick to a spinning ball?🙃

@carultch

2 жыл бұрын

These forces don't make water stick to a spinning ball. In fact, quite the opposite. The apparent centrifugal force is precisely why you think water can't stick to a spinning ball. I assume you are talking about the Earth, because this is a common flat-Earther's talking point. In that case, it is gravity that keeps the water on the Earth, because Earth is a huge astronomical body with 10^23 times as much mass as a typical person, and gravity accumulates with mass. The fact that the Earth rotates, and the apparent centrifugal force due to the rotation, is only a drop in the bucket compared to the strength of the gravitational field. At the equator, the apparent centrfigual force is 0.0334 N/kg (from v^2/R), and the true gravity is 9.81 N/kg (from G*M/R^2), which yields an effective gravity of 9.78 N/kg that you would measure relative to the surface of the Earth. If you are talking about much smaller spheres, like the granite model of Earth in Vancouver BC, that is supported on a fountain's water jet, in that case it is surface tension that keeps water sticking to a spinning ball.

You just have to make sure that wind doesn't cause you problems lol

why stationary air force is not moving things on tray while swinging?

@kallewirsch2263

5 жыл бұрын

for the same reason a moderate wind will not move a glass of water on a table when outside. The force generated by friction (glass standing on table) is stronger then the force generated by the air pressing against the glass. Physics tend to look at effects on a one by one basis and ignoring all other effects in experiments designed to show that one effect. But reality is not so simple. All kind of different effects act together at the same time. Take eg. falling objects. At school you learn the math laws on how to describe that. But in reality there is also another force acting: air resistance. As long as the speed of the falling object is not very high, one can ignore air resistance since it doesn't influence the falling object very much (usually much less then what is measurable in a physics class room). But things get different when the speed gets higher. Skydivers do not fall (in the free fall phase) according to those laws. The difference is the air resistence which increases as the skydiver picks up speed. Why does physics not include air resistance into the laws of falling bodies? Because things then get really complicated. Air resistence is dependent on a lot of things and is not an easy thing to compute.

Yes! First comment :O Keep up the great videos Mr. Yeany!

do this with your hands with a pint of beer in a club it impresses everyone

@grieske

6 жыл бұрын

Yes, it is likely to make a lasting impression on a lot of people, as the tray slams into them. Cool demo, though.

👏👏👏👍🇩🇪

Are there fluctuations in weight?

@Eagles_Eye

6 жыл бұрын

Noel Acosta logically i would say the faster he spins it the more force is applied so the 'heavier' the object same as G force training in those rotating arms if you know what I mean I'm not English

@carultch

2 жыл бұрын

There's no fluctuation in the force of gravity. There is a fluctuation in the apparent weight that you would feel if you were riding on this. What you really would be feeling, is the fluctuation in constraint force, that you instinctively assume opposes gravity, which would correspond to either the tension in the string, or the normal force on the cup, depending on which object you care about.

Wow the like to dislike ratio!

I would have broken so many beakers

8:55

In my day a teacher didn't need to swing above their head an egg atop a golf tee on a tray suspended by strings to get a student's attention!

@YeanyScience

6 жыл бұрын

When was your day?

@PBTophie

6 жыл бұрын

Lol, like 17 years ago. I just meant to comment on the kids' shock when they stopped talking and asked "Is that a golf tee?" That was hilarious. Reminds me of my sister's kids.

Yaw dayı, yaptigin bu deneyleri 300 seneden beri çaycılar yapıyor 😆

Do it outside because sometimes the laws of physics break ;)

Hello there. I like watching you very much but I can not analyze you speaking English. Can you add it to Turkish subtitles? thank you.

@Not.Your.Business

6 жыл бұрын

FIRAT BAYDAR, how could he add Turkish subtitles if he doesn't speak Turkish?

@firatbaydar2669

6 жыл бұрын

Andrei Macaria How do they have their settings, if there is English subtitles, there are Turkish subtitles. thank you for your interest.

@Not.Your.Business

6 жыл бұрын

FIRAT BAYDAR, I think you are using google translate so I'm having a hard time understanding what you mean, but if I understand correctly, you want the auto-translated version of CC. you can easily do that by enabling the closed captions, then clicking on the settings wheel -> subtitles/CC -> auto-translate and select Turkish. but this is not an accurate translation (because of the auto-translation system limitations mixed with the auto-generated closed captions weaknesses), so the only real option would be that someone who speaks decently both languages to add a manual translation... and that person is surely not Bruce. hope this helps, cheers!

@firatbaydar2669

6 жыл бұрын

Andrei Macaria sorry. Are you a girl and a man?

hi sir this is sunil pant from india....still waiting for your reply...

jenga! :)?

Hello

Witchcraft

This looks fake guys

horizontal is dangerous for the audience.

Don't try this at home lol

You met Albert Einstein?!

@YeanyScience

6 жыл бұрын

I wish that were true but he died when I was one year old, I posed with a wax figure

I don't like this. It's so unintuitive but the physics does makes sense!

FAKE! The scene is recreated in CGI smh, look at 1:34 his finger clips through the string, obvious fake, NEXT!

@willbrown4245

6 жыл бұрын

This is the man we should be listening to. Very good charlie, I am very proud.

@charlielyttle8576

6 жыл бұрын

this doesnt make sence becaaause if this is true then we'ds fall off the earth when it spins? but we DONT

@charlielyttle8576

6 жыл бұрын

NEXT!

@willbrown4245

6 жыл бұрын

EXACTLY

@cjkavy2299

6 жыл бұрын

Charlie Lyttle ITS FOR A CHURCH GROUP HONEY!

You should try a clip on microphone

Thanks as always Bruce, great video!