This is like a crash course but nothing about it is too clumped. Perfect, straight-to-the-point, and easy. Will subscribe and listen to you religiously throughout my physics course. Thank you.

@Jai_ShriJagannath

2 жыл бұрын

kzread.info/dash/bejne/dnlqs9idcbKfgdo.html Reason of why static friction is more than kinetic or dynamic friction

this guy carried me through sophomore year chemistry and now he's carrying me through junior year physics

@TravelingTreats

2 жыл бұрын

Same

@floydwynn-jones4043

2 жыл бұрын

so you read Tintin books?

@lestherviceracelocia1119

2 жыл бұрын

@@floydwynn-jones4043 ii

@lestherviceracelocia1119

2 жыл бұрын

@@floydwynn-jones4043 i

@Metamor-phosis

2 жыл бұрын

@@floydwynn-jones4043 i

Professor Dave, your videos got me through physics 1 and 2 in my post-bacc, and as I'm studying for the MCAT I found myself needing additional explanation. The jingle came to my mind and I knew exactly where to go. So thankful for you and your videos!

@carultch

2 жыл бұрын

I think of the formula for heat in terms of mass, temperature and specific heat, when I think of MCAT. Q=m*c*∆T

@Metamor-phosis

2 жыл бұрын

the jingle lol

I did a short experiment. I watched this video 2 times: yesterday night and tonight. Yesterday, I understood everything he said but couldn't get anything inside my head. So I used the whole day today to read the book and solved many maths related to frictions. Tonight as I watched this video again I was able to understand everything loud and clear😁. Thanks professor Dave

Is it sad or impressive Dave can teach in 5 minutes what my professor can’t in 3 3 hour class periods?

@Lucky10279

4 жыл бұрын

Both. Impressive for Dave but sad for your professor and you guys. I'm in the same boat with my professor. His lectures are really disorganized. I was getting a little scared that I was getting confused so early in the semester, especially when I'm way ahead of the math requirements. Watching just a few of Dave's videos and I feel much more confident. I've learned more from from short KZread videos than from 2 hour lectures.

@julianader739

4 жыл бұрын

YESSSSSSSSSSSSSSSSSSSSS

@blinkbubs3994

4 жыл бұрын

dude thats literally what happened to me in class. 3 hour class, dont understand much. i watch this, and it makes a lot of sense.

@Sasukej2004

4 жыл бұрын

@Learn First very true, they want you to know how to do problems and smart students will read about it more at home

@unknownbeing8222

4 жыл бұрын

Am i the only kid watching this...

thanks a lot bro. this new subscriber is from the Philippines, the way you deliver the topic is so smooth, wonderful and easy to understand. thanks a lot. static & kinetic friction topic. great!

Unfortunately, my prof doesn't teach anything... so I am very thankful for your videos with visual aids! I hope you keep making more!!! Yours are by far the best on youtube! :)

@lemondrop8203

2 жыл бұрын

You can't listen, that's why

@AXbcyz

10 ай бұрын

@@lemondrop8203someone’s never experienced a bad teacher

I swear without this video I would be super lost in my physics class

thank you so much for sharing your knowledge with the world :D! now it all makes sense :)!!

7:05 aren't the x & y components mg*csc(theta) and mg*sec(theta) respectively? The trig here isn't checking out for me. ? to denote x-component of mg sin(theta) = mg/? ?*sin(theta) = mg ? = mg/sin(theta) ? = mg*csc(theta)

1:31 "This attractive interaction can hinder motion to some degree" This can easily be taken out of context.

Professor Dave, I have a question! If friction is caused by forces of attraction between atoms on a molecular, and electrostatic attraction is one of of these forces of attraction. Does this mean that friction can change based on the charge of the object?

@qriosiumi2455

Жыл бұрын

Is it specified that the attraction is really electrostatic?

Hello! In the comprehension check you use Fnet= mg sin theta - Ff, I am confused as to why you are using subtraction instead of addition. Thanks!

@ProfessorDaveExplains

7 жыл бұрын

it's true, it could be addition as long as you then make the frictional force negative, we just need opposite signs on the two horizontal forces as they are in opposite directions. in the end, as long as the signs make sense you're all good!

@pubuduweerakoon7174

5 жыл бұрын

There is no certain direction for a frictional force to be acted. It is always resistive to a motion or to an attempt to the motion. When the block moves or tends to move down, frictional force would act up the incline. When the block moves or tends to move up, the frictional force would act down the incline. Thanks.

@Diamondlight04

5 жыл бұрын

Is it safe to assume then, that in problems like these as long as the box is going downwards the frictional force will be negative ?

@phamdung3884

4 жыл бұрын

KB yes. It’s in the opposite direction of the motion so it’ll be negative.

This Guy explained these concepts in just 8 minutes which I am Trying to understand from 2 weeks

thank you so much! you saved a university newbie!

i think there is an error in checking comprehension. if the object is at rest, we wont know whether it moves unless we look at the static friction coefficient (as opposed to kinetic friction as stated)

Lots of new ideas thank you . It's relevant in my study

Your videos are so helpful, thank you so much!

Professor please make a video on tension it is an important topic please make it I love your teachings

thank you man, i am teaching my nephew vectors and this video helps a lot to illustrate parts of the whole idea. thank you.

@Jai_ShriJagannath

2 жыл бұрын

kzread.info/dash/bejne/dnlqs9idcbKfgdo.html Reason of why static friction is more than kinetic or dynamic friction

6:54 I wonder if the Fnet=mgcos(theta)-Fsf resulted in a negative number (meaning the Fsf is greater than the mgcos), then what will happen? Will the box stay at rest or will the box move upwards? Depending on the context though, i'd guess the box would remain at rest.

But Sir how we will know what is the value of cos 35° and sin 35°?

Thanks for explaining i was confused now i understand these topic it helps me to solve jee questions

Thanks,dave. At this current time, i have a hard time learning about frictional force in orthodontic. And ur explanation makes me a little bit confidence. I understand the first 5:30 minutes,the rest remains a question for me. Thx

We could see how much effort you put into creating a video. Super.👍 We A4Q team with your growth. Full support 💪

Thank you, You’ve helped me understand the difference between the frictions.

thank you dave my physics teacher didn't explain in this way as you explained . thank you very much

Thank you so much, I was stuck on a question and this video helped me a lot!

@Jai_ShriJagannath

2 жыл бұрын

kzread.info/dash/bejne/dnlqs9idcbKfgdo.html Reason of why static friction is more than kinetic or dynamic friction

NOW THIS IS CLEAR THANKS PROFESSOR

FYI for people watching this, Fstatic is NOT always greater than Fkinetic. The magnitude of Fstatic depends on how much other force acting parallel to the surface exists. Fstatic can be as much as 0 N if there are no forces trying to slide the object across the surface.

@carultch

3 жыл бұрын

It is mu_static that is always greater than mu_kinetic. N*mu_static sets the upper limit for how large Fstatic can be. Whereas N*mu_kinetic sets what the friction force will be, in the event that there is existing sliding veocity.

Subbed not only because useful information but because Subaru 😎

Thank you man, you nailed it. My teacher can’t even explain it clearly 🙄

Thanks for helping Dave

exactly what i needed before my test! thanks!

Wow..ur teaching is superb with practical learning

Very precise

thank you i really understand friction so easy

How did you get so good at solving, what did you do when you were a student... I want tipsssss as many as the s' s i put

@kazuhiramiller7752

11 ай бұрын

I think he has used calculator. How can someone know the values of sin 35 and cos 35 and use their decimal values in an equation? The equation becomes long and we have multiply big numbers. I think giving angles like 30,45 or 60 is good because their values are easy to work with at the time of calculation.

Bruh, how does this guy manage to learn something that is hard to explain in such ease and how long did it took for him to learn this stuff?

But why does static friction push back exactly as much as I push the object? And why is there a maximum? Why is dynamic friction always weaker?

This is my first video of yours and I subscribed as soon as I saw it at a glance 😊

Professor Dave explains ❤️❤️❤️🥰👍🏻 love this

7:05 No, THANK YOU!!!!!!!

@rossclark6906

4 жыл бұрын

Keanu reeves

I was in tension abt tomorrow's exam but your intro made me free and calm

Can work done against non conservative forces get stored in the form of potential energy?

@ProfessorDaveExplains

7 жыл бұрын

oh man, good question. i can't think of how that would work but i'm sure there must be some example.

@05afnanabdullah87

7 жыл бұрын

Professor Dave Explains​ the Induced magnetic field in a coil is a non conservative field. Still work is stored in the form of magnetic potential energy. Is it the same thing? Thanks :)

@pubuduweerakoon7174

5 жыл бұрын

Can't. That work will be wasted mostly as heat. This is what the meaning of "nonconservative"

@pubuduweerakoon7174

5 жыл бұрын

It is very clear that, any conservative force must be accompanied with a kind of potential energy. But Nonconservative forces are not. By the way, conservative force is defined by the equation of F = dU/dx. Where dU is the differential of potential energy. Work done against a conservative force will result an increase in the kind of potential energy and vise versa. Work done by a nonconservative force will definitely waste the energy which is not reversible as dU. Thank you Sir.

Concepts are simply built...Thanks Sir..

Thank you, Prof Dave! One quick question, As you mentioned Fnet = Ff +mg sinθ But in the last example The solution is Fnet = mg sin 35° - Ff I want to know why it is negative (or you subtract Ff in stead of add) Is it because mg sin 35° and Ff is in opposite direction so that you make it negative? Thank you very much for your effort and I am looking forward to complete the whole series of 43 videos!!:D

@maynur1

Жыл бұрын

As you know, F=MA And the block travels downwards with acceleration "a". Frictional force always opposes the motion of a surface over another surface. So as the frictional force increases, the acceleration of the block decreases. Therefore, the friction force will be negative because it affects the acceleration. And when acceleration is affected, the force will also be affected. This means Fnet = mg sin 35° - Ff.

@SuperCarbohydrate

Жыл бұрын

@@maynur1 Thank you so much for your explanation!! Now I understand more about it!:DDD

But isnt friction also depends on the size of the base of the object? A bigger box will touch more things on the floor a small box will touch less, regardless of the mass. Someone explain

Oh sir... Thanks for saving me ... Actually i love physics but the concept of cofficent "i was unable to understand 8t properly but after you video .. everythings is clear... Thanks sir! !!!!

@carultch

2 жыл бұрын

Coefficient just means a number multiplied by another number. Like in y = A*x^2 + B*x + C, the A and B are examples of coefficients.

anyone know why the kinetic frictional force in the comprehension is being multiplied with the y component of gravity as opposed to the x component?

@HeldanaSeifu

4 ай бұрын

I think it's bc we r finding the acceleration and as the box accelerates the weight cos opp or slow it that's my understanding

Someone can help explain where does 112.4 N comes?

@kazuhiramiller7752

11 ай бұрын

mg sin 35° = 20 (9.8) sin 35° Here value of sin 35 is irrational. He has taken it till 4 to 5 decimal places I think which is 0.5735. So we have 20 (9.8)(0.573)= 112.4(approx) Actually the problem with this question is that how we can find the values of trigonometric ratios of angles like 35°.

6:30 Fnet = Ff - mg*Sin(ceta)

@Mr3mos

4 жыл бұрын

sorry, i'm confused - do we add parallel vectors or minus them from each other? Dave's equation is Fnet = Ff + mg*sin(θ)???

@farhannaufal3697

4 жыл бұрын

@@Mr3mosThe friction is minus because it's a vector quantity and remember that the friction is always opposite. If we define the mg*sin(35)'s direction as positive

@edgarrazelm.certeza1396

4 жыл бұрын

Basically dave is not wrong either you can add it but since the motion is acting in different direction the other one would act as negative and the answer will be net force going to the direction of the larger one👌👌

@250physicst3

4 жыл бұрын

What Dave did is correct. The frictional force is always opposite to the applied force that's why has negative sign and the sine component of the weight is positive because it has the same direction with the applied force

highly recommended☺

Why the examples are not explained by prof? I understood all parts but not the example.

This model works very well for hard surfaces. I wonder how the contact area and other factors start to be important when analyzing friction in deformable surfaces like rubber or human tissue? Would be interesting to know :)

Sir why are we subtracting friction forces from mgsin35 to have friction net force instead of adding to satisfy the static condition of forces in the x- axis

@f-22raptor25

3 жыл бұрын

Friction is in another direction it must be taken away

Hello. I'm just confuse because I read the book named "Conceptual Physics" that says that Increasing contact points doesn't add to the friction. Can someone clarify thanks

@CartwheelPig

3 жыл бұрын

I'm not positive but I think it has more to do with the force of gravity on the contact points than the points themselves. If I have two boxes of the same size on the ground (therefore both boxes have equal contact points with the ground) and one weighs more, the normal force will be greater, and therefore the frictional force will also be greater.

You told that net force is the sum of mg sin theta + friction for but in comprehension question you subtract why

when the mass of an object increases the normal & frictional force increases do the static force increases as well?

Thank you. It helped a lot .

May I have a question. At 1:27 you said the interaction between atoms in the object and atoms in the surface is an attractive interaction. But shouldn't it be repulsive instead? Because the interaction here is between electrons of the object's atoms and electrons of the surface's atoms, both are negatively charged, so they should repel each other instead of attract, right? And if they repel each other, logically this interaction should help facilitate the motion by pushing the two surfaces away from each other. But in fact, motion is hindered. Could you explain how it works?

@kazuhiramiller7752

11 ай бұрын

Atoms that are stable have no net charge. The atom consists of protons as well which cancels the effect of negatively charged electrons. In an atom (which is not an ion) the number of protons and electrons are equal and both of them have the same charge.(i.e charge in a single proton= charge in a single electron) . ( This is 100% true) But the thing is that, even if two charged bodies are interacting still friction will act upon them. Considering that the bodies are big(big enough that we can see them). This is classical physics. Here we deal with objects that are not very small. (Although I am not 100% sure about this one)

when we walk their is a motion so how walking is static friction

Why is coefficient of friction = the angle the object is sliding at? Isn't it determined by the surfaces smoothness?

Professor Dave Explains , The Classic Vintage Intro.

Does the net force depend on the direction of motion if the body or is it always Fnet= mgsin@ + Ff

Professor Dave is my life saver . While my physics professor destroy it😆

@suzuki12334

4 жыл бұрын

How do we decide whats cos and sin at 6:00

@newtube553

4 жыл бұрын

@@suzuki12334 at my channel looke

@suzuki12334

4 жыл бұрын

@@newtube553 kzread.info/dash/bejne/hndmldl9Y5epZ84.html heres what i thought but ty

@carultch

3 жыл бұрын

@@suzuki12334 The easiest way to decide what needs to be sine and cosine, is to inspect the limiting cases. When theta = 0, the sine = 0, and the cosine = 1. Vice-versa happens, when theta = 90 degrees. With your intuition, think about what will realistically happen when the angle is zero, and when the angle is 90 degrees. If the force in question should also be zero when theta =0, then it is most likely going to be sine. If the force in question should be its full amount when theta=0, then it should be cosine. You might have a tangent instead of sine, so also check the other limit. See if it should be cosine, when theta=90 degrees, to conclusively determine that it should be sine.

If you were not on KZread I’d be having a lot more trouble with physics 😅

Can anyone explain why add? 6:27

Me to friction:how dare u oppose me mortal

@mhmthatsmeh

10 ай бұрын

That's hilarious 😂😂 You got some humour ✨

If I wind a rope around a spool body, how many winds do I need to get a frictional grab where it can not slip? Thanks

To be fair, mass is not required to solve the check comprehension problem. Net force equals Fnet = mgsin(α) - μmgcos(α) = mg(sin(α)-μcos(α)). Now a = Fnet/m therefore masses cancel out and we have final formula a = g(sin(α)-μcos(α)).

I have a question: Why is static friction used to walk forward? I know our foot pushes backwards, and the friction lets us go forward, but i thought that static friction only resisted the initiation of motion. Is there an another definition for static friction or am i just not understanding this concept correctly?

@carultch

2 жыл бұрын

It is only locally that static friction opposes the initiation of motion. Locally at the point of contact between two objects. The static friction in this example, is what stops your foot from moving backwards as you push it backwards while trying to walk. If you were on a truly frictionless surface, your foot would slide backwards and you would run in place if you tried to walk. Think of the Earth's surface a "work mirror". You push backward on the ground, by pushing your foot backward while it is in contact with the ground. By Newton's third law, the ground also pushes forward on your foot with an equal and opposite force. The force on the ground by your foot, cannot practically do any measurable amount of work on the Earth, because of the Earth's inertia is so large that its motion due to this force is immeasurably small. Instead what happens, is that the ground reflects this force back to you, through its third law pair of this force, as the ground applies a forward force to your foot, while your body moves.

That fact that I understand friction more by watching him than by listening to my teachers lecture

Super! You made the subject simple! Thanks

You're the best

Thank you for illustrating perfectly

thank you for explaining clearly

In the comprehension check, if the block begins at rest, why don’t we account for static friction before kinetic?

which is correct, is it @6.31 : net force = kinetic friction + mg sin theta or @6.53 : net force = mg sin theta - kinetic friction confused help

@professor_dave_explains do you still stands by the statement that rougher surfaces have more friction?

I fucking love the intro its catchy as fuck😂😂🎉

thanks, really helped

i think its your definition of kinetic friction is very misleading. A car is moving but it is experiencing static friction, not kinetic. Kinetic is only when objects are sliding. When you ski on a car, that's static friction. When there's anti-lock brakes, it prevents you from skidding, keeping static friction there. Since static friction > kinetic, the car will slow down faster if it doesn't slide.

@carultch

3 жыл бұрын

The reason for ABS brakes on cars, is so you can continue to steer while you are braking. A secondary benefit is that you have a greater static friction coefficient than a kinetic friction coefficient, so you can in concept slow down faster. ABS brakes keep the friction with the road in the static friction regime, while the kinetic friction remains in the brakes between the shoe and the drum. If your brakes lock up, and the tires skid on the road, steering does you no good, as kinetic friction can only apply a force that is opposed to velocity. Whereas static friction can apply a force that is partially opposite velocity, enabling you to steer. Static friction is a constraint force that prevents your wheel-road contact from skidding.

thankyou so much bro

How are rubbers treated to loose their friction?

@carultch

2 жыл бұрын

Rubbers as in erasers are not treated to lose their friction. You want as much friction as possible on erasers. Because its ability to pick up pencil graphite is directly determined by how much friction it can generate with the paper.

Sir, how do we calculate the coefficients of friction?

@carultch

2 жыл бұрын

Given what information? Unless you are given the information that allows you to reverse these formulas and calculate the coefficients of friction, there is no way to calculate it from first principles and only the identity of the materials. This is information you look up in a reference table, in order to determine. Or you experimentally measure it yourself.

@NUPUR-t3e

2 жыл бұрын

It is either given in the problem data or we have to calculate by using all these formulas. It is actually experimentally determined & calculated value for each & every pair of materials under loading conditions. Found to be with some variations affected under temperature, surface roughness quality & many more factors. At 11th-12th & undergraduate engineering level only its available values are used. But how actually these values are came which is studied in Masters & doctorate levels with the domains of "Tribology" & "Surface Engineering" under the branches of Mechanical, Materials, Civil engineering & all.

Anyone else confused about the equations at the end? At 6:35 it says Fnet=Ff + mg sin(theta) . . . yet at 6:56, it said Fnet= mg sin(theta) - Ff So which is it?! Do I add or subtract the frictional force?!

@barakatalhinai3541

Жыл бұрын

Bucciarati is physics a jojo reference?? I’d assume you’d subtract since friction goes the opposite direction of applied force

@brunobucciarati7278

Жыл бұрын

@@barakatalhinai3541 physics is definitely a jojo reference. think about Pucci’s stand power to change the physics of gravity 😮 and thanks for the answer!

yes atomic is the root of the constact known as friction. its all part to understand as a whole like an ecosystem. so u can build with perfect natural law in harmony and then we can multiply this to sustain energy. but all this is to be equated in order by function amd presence naturally according to purpose relative to said application. its constant. like anything u cant have just peices and parts but as a whole .

friction may be ionic atomic molecular gaseous liquid solid.

COOL SUBARU CLIP! really piqued my interest. are you a subaru driver, dave?????

Friction does not, depends upon mass,and contact area? How it is possible because as mass and contact area increses their is more adhesion between surfaces of two objects, so more force is required and so equal and opposite reverse friction force operate. Kindly clear my doubt

@carultch

3 жыл бұрын

The unitless friction coefficient is independent of mass and surface area. It depends on the identities of the two surfaces, the conditions of the two surfaces, and whether the friction is static or kinetic. From a first order overview of friction, it is independent of surface area. The surface area ends up "cancelling out" of the equation. The friction force itself, will indirectly depend on mass, because it depends on the normal force, which is usually a reaction force to the object's weight, in some form or another.

I'm not sure if my calculator is messing up but the math in the comprehension seems way off. 20 x 9.8 x sin 35 comes out as 102.5 for me. and 20 x 9.8 x cos 35 comes out as 90.24.???

@ProfessorDaveExplains

3 жыл бұрын

maybe check you're in degree mode and not radians. the video is correct.

@Fuphu

3 жыл бұрын

@@ProfessorDaveExplains Yeah you're right. Thanks. Surreal getting a reply from a role model.

@kazuhiramiller7752

11 ай бұрын

​​@@ProfessorDaveExplainsI don't even know how to find values of trigonometric ratios for a particular angle in the calculator so I have to calculate on paper. 😅

6:58 I almost got it right tho, I just forgot to calculate the sin of Its Normal Force which I didn't understand before the answer was shown.

What is the maximum coefficient of friction?

@heinrichpreussen

2 жыл бұрын

Metals on themselves usually have a high coefficient.

Thankyou Professor Dave!

Question - how can F=ma if F is a variable? In a previous video we see how a puck requires very little force to move across ice, but put that same puck on sandpaper and it'll require more force to move it in the same manner. Is it just that when dealing with additional forces such as friction, "F=ma" becomes Fnet=ma?

@carultch

3 жыл бұрын

It always is Fnet = m*a. We just get away with omitting the subscript of "net" when we are only dealing with one force that makes a difference in the object's acceleration. When the puck moves across the ice, there are two significant forces which you ignored completely. Namely, the weight of the puck, and the normal force of the ice pushing upward on the puck. These forces add up to zero, by the nature of the normal force, since the normal force will be as large as necessary within the strength of the materials, to prevent penetration. Because these forces add up to zero, they cancel out of the equation of Fnet=m*a.

@kazuhiramiller7752

11 ай бұрын

Definition of force is that:- F=ma

He said "to get the net force you add the forces parallel to the surface" but in the comprehension he subtracted😭

@ProfessorDaveExplains

2 жыл бұрын

No I added, but the frictional force is negative.

@SacredLover21

Жыл бұрын

@@ProfessorDaveExplains why is it negative?

@user-yw1rw8tj5s

9 ай бұрын

Because the opposite direction causes the force to be negative in value. That’s why net force can be 0, which happens when the parallel forces on each side are the same.

@user-yw1rw8tj5s

9 ай бұрын

Frictional force is an opposing force, which is in the other direction

Hello, love the videos! Just a quick problem I'm having in the comprehension section though. Just before comprehension, you say that cos theta and normal force cancel each other out so to find the net force we just have to take the sum of the frictional force and sin theta. But, then in the comprehension section you solve suing cos theta instead of sin theta. Should cos not have cancelled out with the normal friction and as such not even be a part of the solution? I used sin 35 instead and got 0.325m/second^2 as my final acceleration and I'm not sure why this isn't correct

@thecurvycurator8828

5 жыл бұрын

*using

@thecurvycurator8828

5 жыл бұрын

Lol nevermind just figured it out XD

@garickmendezpadilla8133

10 ай бұрын

how did you figure it out? lol got my exam tomorrow@@thecurvycurator8828

Wow thanks alot ,it was really well explained

Great explanation - thanks