Angular Motion and Torque

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@@ProfessorDaveExplains I hope you will also release some of the grunge or guitar learning tutorials in soon

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I like the way that you actually explain what torque is and not just how it is calculated

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i love how he gives us real life examples of usage of torque instead of just telling us that it's a thing that exists that we simply have to accept immediately

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"Clocks are negative" is how my textbook said to remember that clockwise motion is negative and hence counterclockwise is positive.

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[@JoséAntonioBottino]

My guess is that actually the angular speed ω is not measured in rad/s but in (rad/rad)/s = 1/s. If we say that the measure β of the angle is θ radians, we mean β = θ rad, and θ is the number of radians (it does not have the unit "rad"). For emphasis we can say that θ is measured in rad/rad = 1, since θ = β / (1 rad) and θ is a dimensionless variable. When we use mathematical formulas to obtain formulas in Physics, we have to know what the variables represent. What I consider a mistake, is present in the literature, it is not only in this video. Therefore, I will leave another comment with the detailed information to be examined.

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[@heretocomment2337]

Hi @ProfessorDaveExplains I have a few questions about torque that I don't know if you already covered in this video, because to be honest, I didn't watch it all, but you are the only one on youtube making videos on this topic that replies. Here are my questions: 1. What absolutely decides whether rotation is clockwise and anti-clockwise? In a 3D spinning item, such as a bicycle wheel or even a ferris wheel like you said, has 2 sides. On one side, no matter how it spins, it will be clockwise, and the same wheel will appear to be anti-clockwise when viewed from the other side. 2. How does torque have a direction in or out of the page? I know the right hand rule RHR, but it doesn't explain anything. Taking the bicycle wheel or the ferris wheel as an example again, think about the axle: when looking at the wheel from the side so all you see is a thin rod, the axle sticks out on both the left and right, but when applying the RHR, and you pick a side, any side, your thumb will invariably end up pointing at either one of the left or the right... it's just a matter of which side you choose. Further, even if the sides don't matter for points 1 and 2 because the mathematical signs will reverse which ultimately end up cancelling, what does it mean when people say torque has a direction in or out of the page? If a spoke in the bicycle rotates as the wheel spins, it spins either clock or anti clockwise depending on how you look at it. The force applied to it is perpendicular to the spoke on the same 2D plane as that of the flat surface of the wheel. However, if you used the right hand rule, your thumb will point in either direction of the axle that sicks out. But that's not where the force is, you are not pushing on the wheel from the side (remember we are looking at the wheel from the side so we only see the thin profile of the wheel tread and no spokes). What is there? How can you say that "torque comes out or into the page/plane" when torque is the force you applied to it (eg to the spoke) to make it turn? Thank you in advance and sorry for the long question.

[@lagartijaterrorista6943]

1. Nothing decides wether rotation is clockwise or anticlockwise,,, it is not an inherent thing of the universe (there’s not one right way), positive and negative is just the convention scientists chose. As you said, it depends on where you are looking from. So when doing exercises, the exercise will tell you where you are looking from. And in the example of the bicycle wheel, if we consider a bicycle in a 2D motion from left to right, using the right hand rule will give you the same result for torque’s direction wether you look from one side or the other (it is into the page) (remember to use the right hand, seems obvious but i’ve fucked up on that before🕊)

[@JoséAntonioBottino]

Many people wonder why radians do not appear when we have radians*meters. Here is an attempt at an explanation: Let s denote the length of an arc of a circle whose radius measures r. If the arc subtends an angle measuring β = n°, we can pose a rule of three: 360° _______ 2 • 𝜋 • r n° _______ s Then s = (n° / 360°) • 2 • 𝜋 • r If β = 180° (which means that n = 180, the number of degrees), then s = (180° / 360°) • 2 • 𝜋 • r The units "degrees" cancel out and the result is s = (1 / 2) • 2 • 𝜋 • r s = 𝜋 • r that is, half of the circumference 2 • 𝜋 • r. If the arc subtends an angle measuring β = θ rad, we can pose a rule of three: 2 • 𝜋 rad _______ 2 • 𝜋 • r θ rad _______ s Then s = (θ rad / 2 • 𝜋 rad) • 2 • 𝜋 • r If β = 𝜋 rad (which means that θ = 𝜋, the number of radians), then s = (𝜋 rad / 2 • 𝜋 rad) • 2 • 𝜋 • r The units "radians" cancel out and the result is s = (1 / 2) • 2 • 𝜋 • r s = 𝜋 • r that is, half of the circumference 2 • 𝜋 • r. If we take the formula with the angles measured in radians, we can simplify s = (θ rad / 2 • 𝜋 rad) • 2 • 𝜋 • r s = θ • r where θ denotes the "number of radians" (it does not have the unit "rad"). θ = β / (1 rad) and θ is a dimensionless variable [rad/rad = 1]. However, many consider θ to denote the measure of the angle and for the example believe that θ = 𝜋 rad and radians*meter results in meters rad • m = m since, according to them, the radian is a dimensionless unit. This solves the problem of units for them and, as it has served them for a long time, they see no need to change it. But the truth is that the solution is simpler, what they have to take into account is the meaning of the variables that appear in the formulas, i.e. θ is just the number of radians without the unit rad. Mathematics and Physics textbooks state that s = θ • r and then θ = s / r It seems that this formula led to the error of believing that 1 rad = 1 m/m = 1 and that the radian is a dimensionless derived unit as it appears in the International System of Units (SI), when in reality θ = 1 m/m = 1 and knowing θ = 1, the angle measures β = 1 rad. In the formula s = θ • r the variable θ is a dimensionless variable, it is a number without units, it is the number of radians. When confusing what θ represents in the formula, some mistakes are made in Physics in the units of certain quantities, such as angular speed. My guess is that actually the angular speed ω is not measured in rad/s but in (rad/rad)/s = 1/s = s^(-1).

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sir Dave,nice video for understanding the conept

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[@heartofblackonyx]

there is a right hand rule for keeping track of positive or negative rotation that is much more robust and systematic than what he describes.

[@tlotlisogladwinmore3603]

When the video start I was sleepy, but as you arrive at Torque I stood up. KEA LEBOGA.

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You really explain it well Sir....I was stuck in this concept like forever until I saw your vid thanks for the vid ❤️❤️❤️❤️...

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Guess who has their exam tomorrow?

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try setting it to 0.75 speed if you need more time

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Thak you!! Great video!! I was really happy to find info about inbetween perpendicular applied force and parallel applied force for torque

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your awesome dave

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good explaination

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Very good explanation Sir.., thank you

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Ap phys 1 cram be like

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Ok so what does the 9.8 represent

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Gravitational acceleration

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Thank you made me understand this,but sometimes are too fast when explain other topics like momentum

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That transition at the end tho lol :)

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3.3 mtr

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amazing video

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Sir please also give us some more questions which are in HOTS so that we can know how to apply those concepts ! Thank you sir

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You are the best!!!

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Thanks dude, this was great!

[@kostasbaganas3681]

FYI: π is not pronounced as 'pie' in Greek, but more like a 'pe' instead. The same holds for the wave function in Quantum mechanics ie. 'pse' instead of 'psie'. Also, torque τ is read as 'taph' (or 'taf'') instead of 'tao' ('taou').

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im not interested in learning pronunciation

[@carultch]

In English, we have to shift the vowel when we say the letter π. Otherwise it would sound identical to the Latin letter p. It is a consequence of the great vowel shift in the history of English. Other languages that use the Latin alphabet, call the letter "pay", instead of "pea", and can retain the original Greek name of π, and still tell them apart.

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[@NatalieNguy]

Hi - do I deduce correctly from your introduction (at 0:57) that uniform circular motion is translational motion? I quickly looked it up and one source says uniform circular motion is not translational motion, but rather a special form of rotational motion. I'm a bit confused with the new term "translational motion" in the context of your introduction. Can you please offer some explanation?

[@carultch]

There are principles from both branches of classical mechanics, that apply to uniform circular motion. You can apply both the translational concepts to it, as well as the rotational concepts to it. The term translational motion, just means that it is based on moving the object in its current form from position A to position B, without rotating it, extending it, or flipping it. If an object were in pure translation during uniform circular motion, this would mean that one side of it constantly faces a fixed direction. So imagine painting a ball with half of it red, and the other half blue. Move it in a circular path, while a friend is watching you. Arrange it, so that the blue side always faces your stationary friend. This would be uniform circular motion in pure translation. This usually doesn't happen, because it is a lot easier to create uniform circular motion in a way that it coexists with rotation at the same rate, such that one side of it constantly faces the center. It is a lot easier for you to rotate the ball, so that the blue side constantly faces you, rather than so the blue side constantly faces your stationary friend.

[@kavyahegade6477]

I like the "TAU" you pronounce😃🤪

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Your videos are very helpful.I am your student from India.keep uploading videos for physics as well as chemistry

[@kishankumar9068]

Sir, please make videos on moment of inertia

[@ProfessorDaveExplains]

check out my tutorial on newton's first law of motion!

[@suzumii2998]

sir the unit of torque is NM that is joules. so work, energy and torque are the same quantities?

[@vanshikashah6119]

thx helped

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I really understand u r explanation is well good

[@babe3736]

But what did Archimedes say next

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thanks

[@bibilihills5062]

In the last question why net torque must be zero?

[@fortniterpro3397]

Wonderful

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This video is awesome and easy!!

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In jail, I could open the big metal doors with my hand right next to the hinge. Nobody else could.

[@moontonaccount9489]

Hey, would't the lever that will move the earth be faster than the speed of light since it will transfer force faster than light? So it will mean that something can travel faster than light?

[@shaherfurany3926]

in your example the rod was horizontally placed , what if the rod was vertically placed ? then the force ( torque) will be perpendicular to the rod and consequently sine turns into cosine ??

[@anaghaanagri2159]

It's always sine theta because theta is the angle between the force (torque) and the plane of rotating object (in other words , the displacement vector )and not the angle between the force with the horizontal. Torque is force times the perpendicular distance between the force and plane of rotating object.

[@daniealalexgender3567]

Angular momentum Pura clear ho gaya