I have to learn this in 6th grade sigh

@@King-fr4bd same lol

Exactly😄

@@Ice-tx8kc i love you

Everything?

Right

You all probably dont give a damn but does anybody know a tool to get back into an Instagram account..? I was dumb lost my password. I appreciate any tips you can give me.

@Elisha Vincenzo instablaster ;)

amen

I agree but be nicer

You need to control your self my lady find a good doctor before* is too late...

You are right. Him and Organic chemistry tutor

​@@Triptocrete bruh you care too much about some commenter in the internet, go get some sunlight. (Dont forget to like the video 😂)

The buoyant force is more than the weight force. This is just an introductory video, so that's all that matters. Your teacher needs to take a chill pill

fuck poo

Can always play the video in class too. Everyone loves a video break and visuals

Lmaoo

Really? I'm gonna do it

Things that float are boyant

Yeah I got confused

The water is more dense than the object that is displacing it. They will have equal volume, but not equal weight. That's what creates buoyancy, since the buoyant force is equal in magnitude to the weight of the displaced fluid. It's not equal to the weight of the object.

If they were equal, the ship would sink right up until it was completely submerged

Lol 😂

That's right, the explanation is very easy to understand

Think about it like this. An empty water bottle floating in a sink is raising the water level of the sink by a tiny amount proportional to mass of the bottle. If you push it under water the water level increases a lot due to it displacing the entire volume of the water bottle. Now imagine filling the bottle with water from the tap and pouring that water into the sink. The water level will increase exactly the same amount as when the empty bottle was forced under.

@gurman lall Seriously, I'm a physics student who kept studying a lot to principles and the concept of buency never I had a grasp for, until this video.

f

there isn't really too much to say about them, they just list a bunch of possible transformations. it's like someone took a bunch of lecture notes and condensed them into an image. they can definitely seem overwhelming! it just shows you ways to transform different functional groups and what not.

@@ProfessorDaveExplains tnx

yes and yes! water is 1.0 g/cm^3

While he did develop a test to determine the volume of an object of any shape by measuring the water it displaces, his "eureka" moment was when he figured out that the same principle (the displacement of water) causes objects to float. A floating object displaces a volume of water with a mass equal to its weight.

those are coming soon!

Well, that means that heavier floating objects will displace greater amount of fluid

@@Adecto so? Elaborate

When an object is floating on the surface of a body of water, the volume of the object below the surface is equal to a volume of water with the same mass as the entire object. For example, if you put a block of wood with a mass of 3 kg in a bucket of water, the volume below the surface will be 3 L (or 3,000 cm^3), because that volume of water has a mass of 3 kg. Now suppose you make the block heavier by putting a 100 g weight on top of it. The block sinks slightly further into the water until it has displaced 3.1 L (or 3,100 cm^3) of water. As long as the weight of the object is equal to the weight of the water it displaces, it will continue to float. If its weight is ever greater than that of the water it displaces (i.e. if it's denser than water), it sinks.

You are right. He has it wrong. The ship does NOT weigh less than the water it displaced.

I agree. The ship's weight and the weight of the water it displaces are equal. That's basically Archimedes principle. I had an exchange with professor Dave on this very comment section a couple of months ago on the subject and he wouldn't admit he was wrong. I guess you could find it. It's worth a read.

If that were true, when you pushed a beach ball into the water, the ball would stand still and not float back to the surface. If the air was water we could say the ship would float into the air... Basically: The force will just stop being applied onto the ship after the ship is out of water Moral of the story: Sober up before studying physics (jk, Dave could explain it better with an animation of interaction between the water particles and the ship )

The first f(b) is the formula for the buoyant force, and the second f(b) is the sum of the gravitational pull and buoyant force, which is the effective acceleration an object experiences at rest, and it shows how buoyancy 'reduces' the pull of gravity. (note that I said at rest because if the object is moving relative to the fluid, drag and lift forces will also occur)

but then you got to all the amazing knowledge and you couldn't believe it, right?

Oh yeah! Thanks! wish you could make one about bernoulli

Kilograms (kg) are a unit of mass while Newtons (kg * m / s^2) are a unit of force. The difference is that a given object always has the same mass, but its weight (the force of gravity) depends on what objects are pulling on it and how far away they are. For instance, if you took a 5 kg object to the moon, it would still have the same mass (5 kg), but only about 1/6 the weight it has here on Earth (8.125 N vs. 49 N). Mathematically a force is a mass times an acceleration (F = ma). On the surface of the Earth the acceleration due to gravity (g) is approximately 9.8 m / s^2. Multiply that by the mass of an object and you get the force of gravity acting on it in Newtons.

The unit of Newtons are introduced, in order to make Newton's second law equation work elegantly and simply. Fnet = m*a. Since acceleration has the units of meters/second^2, and mass has the units of kilograms, then Fnet needs a unit of kilogram-meters/second^2, which we define as the Newton. Since Earth's gravitational field is not equal to 1 m/s^2, an object's weight in Newtons is not equal to its mass in kilograms. When kilograms and grams are informally used as weight or force units, they refer to weight in Earth's gravitational field. 1 kg-force is defined as 9.80665 Newtons, and 1 gram-force is a thousandth of this value. The value of 9.80665 N/kg is used, because this is a representative average of Earth's gravitational field.

If p(object) < p(fluid), the object, will float. If p(object) > p(fluid), the object will sink. The volume of water displaced by a sinking object is equal to the volume of that object. This means: Fb = pgv Where: Fb = buoyant force p = density g = gravity v = volume of displaced fluid

I did but nobody listened to it so I stopped!

@@ProfessorDaveExplains whaaat! I never knew about the podcast... maybe it was not advertised enough 😑☹️

It's a constant of this planet. It is the Earth's gravitational field strength.

it's a constant, acceleration due to gravity on earth.

Yes. The buoyant force (like all contact forces) is caused in large part by molecules repelling one another. A hydrophobic substance repels water more strongly than most other substances.

@@wizardsuth ah ok thank you for the explanation

The buoyant force is a reactionary force to gravity.

Because the buoyant force is a reactionary force to gravity.

@@ProfessorDaveExplains thank you so much, for prompt reply 😊 you're doing great work 💯

@@itsmrbrightside179 Buoyancy works like an inverted Atwood's machine. There is coupled motion between the displaced parcel of fluid equal in volume the volume of the object immersed, and the object itself. But instead of interacting through tension in an overhead string, like the coupled motion between the masses in Atwood's machine, an object in water interacts through the differential hydrostatic pressure of the water nearby, and the displaced water also experiences buoyancy from the rest of the water body. Instead of the pulley in Atwood's machine, you have the pressure on the water from the bottom of the container, that supports the entire body of water.

hmm, well the weight of an object should not matter whether it is in water or on land, as weight is simply determined by the mass of the object and the strength of the gravitational field

so, it doesnt matter what the different weights are in a situation. you just have to find the mass and times that by 9.8

yes mass times g is how you calculate weight in any scenario

ok, but why in other videos they say to times the volume times the density then times by g to find this buyont force

or to take away different weights

arnav is is you?

unfortunately no that was the last stuff for motion, i'm moving on to thermodynamics, but feel free to email me with questions!

oh no! Torque is a very important topic in classical physics, please try making just one video if you can manage time.....People may wonder how the rotation of engine shaft/ turbine has changed the world so far and things would get more clear with your knack of explaining things simply!

oh i did release a video about angular motion and torque yesterday, did you see that one? i thought you were asking if i would do more on that subject on top of that tutorial.

uh-oh... sorry professor, I didn't notice! you already posted a video on torque... thanks as always

I upvoted your comment! Yay!

Fill a bucket with water up to the brim, then stick your arm in all the way to the bottom. The displaced water is what sloshes over the sides. To put your arm in the water, you have to displace (push aside) a volume of water equal to the volume of the part of your arm that's under the water. If the bucket isn't full, the water level rises as you put your arm in. Making the water move upwards like that requires you to exert a force, and the water pushes back with equal force.

Nooo

Archimedes principle is the method for calculating the buoyant force in a situation of fluid statics. Buoyancy or the buoyant force, is the upward force an object experiences by virtue of being immersed in a fluid.

It doesn't. Water tends to coalesce into a sphere due to the electrical attraction between water molecules. Objects don't have any particular tendency to float or sink in it.

Yes, as a matter of fact there is. Consider a cubic meter box, immersed in a deep lake, with water pressure on all sides of it. To make the math easy, assume water's density is exactly 1000 kg/m^3, g is exactly 10 N/kg, and the ambient pressure at the top of the lake is exactly 100 kPa. Place the top of the box 10 m below the surface. This will mean that the top experiences 200 kPa of static pressure, and the bottom experiences 210 kPa of static pressure. The force on the top of the box is therefore 200 kN downward, and the force on the bottom of the box is 210 kN upward. The net force from the water thus far, is therefore 10 kN. Do we need to consider the sides? Well, there will be hydrostatic pressure on the sides of the box, but any pressure on the left side, will experience equal and opposite pressure on the right side. Same with the front and back sides. So pressure on vertical surfaces will add up to zero. This allows us to conclude that the net buoyant force is 10 kN. According to Archimedes principle, it should also equal the weight of 1 cubic meter of water. 1000 kg/m^3 * 10 N/kg = 10 kN. And look at that, both methods agree and get the same answer.

If you take a neutrally buoyant ball that is equal in density to water and completely rigid, and immerse it in incompressible water, then it will neither float nor sink. It will remain at the initial position you placed it, and if you give it an initial velocity, it will move at a constant velocity, since the forces add up to zero. In reality, no object is infinitely rigid, and water isn't perfectly incompressible. If the solid object is more flexible than the water in its ability to change volume under pressure, then this will be an unstable equilibrium. If the object descends, then it will experience more water pressure and compress, thus becoming denser than water, which will cause it to sink. If it rises, then it will experience less water pressure and decompress, thus becoming lighter than water and floating. This is the working principle of Cartesian divers, where you can compress a water bottle and make the divers descend. And counteracting this instability is a major design challenge for making a submarine neutrally buoyant, so it can hover in water. By contrast, if the object is more rigid than the fluid, then the equilibrium will be a stable equilibrium. As it descends, it experiences a denser fluid that causes it to float, and as it rises, it experiences a sparser fluid that lets it sink. This is why objects that are buoyant in air, will naturally rise to a cruising altitude, where they experience a stable equilibrium, because air is a lot less uniform in density than its liquid counterparts. So blimps and balloons have no trouble achieving a stable flight in air, unlike submarines in water.

@@carultch oh damn thanks, that was really helpful

They cannot.

what question

Um, answer to what?

@@ProfessorDaveExplains he made another comment with the question

We don't know the density of the ball.

that's a great to way to think of it! except you must see that there is indeed a force being exerted, the buoyant force, in the same sense that a chair exerts a force on your body, the normal force. but your conceptualization is indeed sound.

Only in the sense that the electrons of any object repel the electrons of any other object. There is nothing inherently special about boats or water or buoyancy in general. Explaining it as its own unique force is very confusing. There is only gravity and electron repulsion at work. The resulting "buoyancy force" is merely a side effect of gravity pulling harder on the water than on the boat. I'm trying to give you constructive feedback and also help everyone else who might be reading. I looked through a whole bunch of buoyancy explanations and they never once mentioned this. They just say "boats float because of the buoyancy force" and never explain what that is or where it comes from or how this even works. They all make sure to mention the boat must weigh less than the water or it will sink, but not why this is important.

well yes, but in this way all the forces we discuss in classical physics are actually just other forces in disguise. the frictional force is a manifestation of the electromagnetic force. centripetal force, normal force, the tension of a string, none of these are fundamental forces. but they are excellent descriptors of phenomena, so we still use these terms.

His comments aren't ridiculous in the slightest. He's right; a boat's flotation is entirely due to gravity acting more greatly on the more dense water than the less-dense boat thus displacing the boat upwards to a point of equilibrium.

@@Anon-gx6ih I think you've got the concept. If an object displaces some of the molecules in a fluid, others are effectively pushed upwards against gravity, and this causes them to push back with equal force. Although buoyancy is caused by countless molecules interacting via electrical forces, in physics we tend to simplify our models by looking at the net effect, which is an upward force exerted on the object by the fluid. Indeed, Archimedes figured this out before anyone knew anything about electrical forces or the internal structure of matter. One clever fellow, that.

I did. It's the reactionary force to gravity.

@@traversniemi5342 No friend, it is you who need think things through more carefully.

No, that's correct.

If the ship weighs less than the water it displaces, how much less? Surely it's the same.

@@captainoates7236 I don't know how much less. It's an imaginary ship. But it weighs less than the water. That's how it floats. If it weighed more, it would sink.

Any object, wholly or partially immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object. The statement above is a description of the Archimedes principle copied and pasted directly from the wikipedia article on buoyancy. I apologise for trying to correct you as you are far more qualified than I and I know wikipedia is not completely reliable but the operative word here is 'equal' and not 'less' whether the body is floating or not.

@@captainoates7236 If you are having trouble comprehending the sentence you just pasted, I suggest watching this classical physics series from the start.

Pagal kàhi ka

yes, but the latter two are not really of interest unless discussing particle physics

Yes. And there are buoyant forces in plasmas as well. If you were an astrophysicist studying the sun, you would be calculating buoyant forces in plasma as the surrounding fluid. However, introductory examples tend to stick to situations that most students can easily relate to here on Earth, and therefore stick to buoyancy in liquids and gasses. There are ways you can make buoyancy occur in solids, and Bruce Yeany has experiments that show it occurring in agitated sand.

Good thing.

check out my general chemistry series! everything you need is in there.

Professor Dave Explains tq I will do it thank you will u be my physical science teacher online?

of course, that's what my channel is for! to help you with everything you need to learn.

Professor Dave Explains thanks sir .the way u explain me I'm ur biggest fan ...I will not leave u .tbh I am like eww phy I hate but now I love physics bcz of u thank you sir now tym to sleep tomorrow my physical science exam is there thanks sir u helped a student who is in need thnx

Typical Indian...

It isn't due to Newton's third law, but otherwise you're right. The water has weight due to gravity. If you displace some of it, the volume you displace is forced upwards against gravity. The displaced water pushes back with a force equal to its weight. We call this upward force buoyancy.

The buoyant force occurs because of the pressure gradient in the fluid. Pressure (relative to surface atmospheric pressure) is proportional to depth below the surface, for a fluid of uniform density. This causes a stronger force of fluid pressure at the bottom of an immersed object and a weaker force at the top. The difference between the two pressure forces on the object, yields a buoyant force.

@@carultch Wow Thanks! I've always wondered why buoyant force acted in the first place. You have answered 28 year long life question. XD

@@jomarico1770 No problem, glad I could help. Another way to think about it, is that buoyancy works like an inverted Atwood machine. It's coupled motion between the immersed solid, and the displaced fluid, because the displaced fluid has to move in exactly the opposite direction as the solid. And they both interact through the buoyant force, that maintains this coupled motion. Mass 1 is the displaced fluid, and mass 2 is the immersed solid. Except instead of a pulley, we have the bottom of the container pushing up on the entire fluid medium, and instead of the tension in the string, we have the fluid pressure as it interacts with the immersed object.