Friction - A Level Physics

[@boum62]

Fantastic lecture. So interesting. I gave up sciences in my 3rd year. Now my scientifically minded son sends me these links so he and his big sister can discuss their studies with their thicko accountant dad. The great thing about you tube is that the best teachers are available to all. Thank you for your time.

[@abrar__sami]

your voice is clear, as an unattentative student I need a teacher like you whose explainations would stick to my head all day, I love how you explain too

[@DrPhysicsA]

For the purposes of A-level physics, friction is solely determined by the normal force and the coefficient of friction which is unaffected by acceleration.

[@saintbelt]

You sir are a living legend. Saved my ass. Better than all of my lectures combined.

[@DrPhysicsA]

You might want to look at my videos in my Quantum Mechanics playlist and in particular at the one on "The Wave Function". If that doesn't help feel free to leave your question in the comments section of that video - tho I can't guarantee I'll be able to answer it.

[@brockobama257]

idk how to convey how thankful i am for your videos within this youtube comment, so THANK YOU KEEP IT UP MATE

[@lelet6139]

I am a physic teacher. I really like your videos in this series. your videos are very useful for my teaching lesson

[@sliderulelover]

Outstanding presentation! Bravo! You cover all the important aspects of friction, gravitational force, Normal force, and coefficient of friction. Very well done!

[@DrPhysicsA]

My understanding is that one mass is on top of one another mass forming a single total mass M. They are on an incline of angle a. The force acting down the plane will be F=Mgsina. The maximum force acting up the incline is uR (u = coefficient of friction, R = normal force = Mgcosa). The value of u doesn't change (apart from the distinction between u associated with getting the mass to move and u once it is already moving). But the frictional force will stop movement till angle a is large enough.

[@anchalyadav212]

u are great u hav helped more than my physics teacher in my school

[@paddyshanahanmathematics6918]

"let me just draw that alpha betta"

[@mikeoxlong2077]

Lmao

[@cg77539]

A good job...I always look for the additional info given at points that helps students dispel questions and was pretty complete in that regard...would suggest mentioning more about the fric. coefficient and its tabulation in science--that there are established values in tables that are consulted by designers.

[@DrPhysicsA]

Well music and physics do go well together.

[@jilljill73]

many thanks for the help! it is really great to follow your clear, detailed, concise presentations.

[@awolgeordie9926]

I will be teaching A Level Physics soon and all your videos in this series have been invaluable so far. You're a top man Bob!!

[@DrPhysicsA]

Thank you. Very kind of you to take the time to say so. All good wishes for the teaching.

[@Realthx]

acceleration not only speeds up and slows down, but is needed to turn objects, the resistance you feel to the movement is the force applied by the acceleration needed to turn the car, once again f=ma, but in the opposite way to the force turning you (for every action, there is an equal an opposite reaction.) your turning right, you feel a force pushing you left

[@DrPhysicsA]

Thanks for kind comment. I hope its helpful.

[@thesmellofnewpages]

This is an excellent video, It has really helped me with understanding IB Physics HL. The only video out there explaining things properly. Thank you very much!

[@moatta]

An overall explanation for the friction, thanks alot helped me in the exam

[@michelebianchi7861]

Do you always do your laundry while making videos, I can always hear the machine spinning in the background?! xD btw hands down the best physics teacher on youtube !

[@juniyasteffi3790]

srsly!!!! i cudn't gv hear to tht cuz here i'm sitted next to the laundry room and....the washing machine here too is spinning with tht HORRIBLE NOISE [LMAO]

[@abithampi9474]

BTEC student, trying to learn A level physics for an entrance exam; glad to say I found your videos, altho I may still be screwed XD

[@raysgotacatuphisarse]

i wish this guy was my physics teacher! he makes it all easy to understand!

[@Tonicwine999]

Fantastic, great explanation too. Thanks

[@hallojimmy]

hi sir, my question is if there is a mass inclined to a slope at a angle and if another mass is put on top of the first mass would the u (in friction = uR,) ever change? I first thought was on question was, no it doesn't as its always constant, for any masses placed on the same surface. However, in my mechanics 1 exam paper, one of the question asked me find the range of values of u. I would be glad to hear your thoughts on this. Thank you

[@PsyMongazoid]

This is great. I was shit at physics at school but followed this well enough.

[@talzO9]

at 8:22 how is that angle Alpha? How do you determine that that would be Alpha. Isn't Alpha the angle of the incline at the start? I am stuck D:

[@Raindeux]

+talzO9 They are related triangles. If you rotated the incline positive 90 degrees that is what you would get. Draw it on paper and see for yourself. They are equivalent angles.

[@talzO9]

Raindeux ahh :D i see. Thanks!

[@varunpanchmal8762]

At 17:38 . Mg>mgSin(Aplha) + Ffmax . So shouldn't Mg move down and not up because its greater?

[@DrPhysicsA]

Varun Panchmal The arrow refers to the direction the block on the incline will move.

[@laurenceschon3628]

wooow you are so good at explaining thank you SO much!

[@Aeghamedic]

A larger mass is more resistant to changing its motion, which includes direction. Say m1=m and m2=2m, where m2 is the mass of the larger car. If F=ma, then F1=ma and F2=2ma. To turn in time and not drive off the road, a must be the same. So, doing algebra, F2/2m = F1/m. Solving for F2, we get that F2 = 2F1. This is why larger cars are more reluctant to turning, it requires more force but the engine is limited. For circular turning, a = (v^2)/r where r is the radius. So, F= m(v^2)/r

[@Realthx]

um... f=ma, the bigger the mass, the bigger the force required to make it accelerate to the same speed, and the larger force to change its direction? i dont really know what your asking, inertia refers to the resistance of acceleration. So the Fmax value of friction applies and the weight of the object applies, but again, your question was vague

[@physjim]

could you explain or point to some source about the reason behind the "toppling" principle and the line crossing the base or not. Intuitively is seems reasonable, but it would be nice to see it more rigorously.

[@betterffd]

Great supplemental material. Lord knows I'ma need it, especially with my instructor. x_X community college...

[@cryptoboy9943xxz]

I remember the time when i discovered the power of friction. My son was born 9 months later.

[@celaenas3016]

newtons 3rd law states that the force that is equal and opposite to the force applied (reaction force) stays equal and opposite, even in motion. This explains why an object accelerates to the ground. The air resistance (which is not the equal and opposite force of the object's weight) is unbalanced by the weight force, but this doesn't violate the 3rd law, as the opposite and equal force of an objects weight (the Earth's weight) is still equal and opposite to the object's weight. What you said about friction is correct but it isn't the equal and opposite reaction force to push, it is to thrust though.

[@celaenas3016]

the push applied and the friction are not an action-reaction pair, as you wrongly stated. It is the friction of the book on the table, and the friction of the table on the book that are equal and opposite in magnitude and direction.

[@TheRealFOSFOR]

Not that it has anything to do with the math, but I think the friction is nothing but microscopic irregularities that stops the movement at any direction. Like a saw digging in to a piece of wood. (really bad example of what I'm thinking here) The object wont budge until it breaks the "peaks" of the irregular surface and after that it has momentum to more easily brake the following "peaks"... It is hard to push on the saw when it is stationary in the wood put when you finally get it moving by pressing really hard it will slide with ease. The point I'm trying to make here is that it sounds funny to say that "the saw" pushes back more and more while I try to make it move. It is really just the wood that waits to be broken. I made a fool out of myself didn't I?

[@betterffd]

+He Ka A microscopic irregularity that hinders movement definitely sounds like a force of friction to me.

[@TheRealFOSFOR]

# Sq_One exactly.

[@Linaker22]

"Bookcases do not suddenly go upwards." Quote of the day.

[@chend7948]

keep it simple, keep it clear. too much exciting examples will be confused to some ppl.

[@xIKieeranIx]

Is this the same as if the mass was being pulled up the incline by a person by a rope? so there is an angle of the rope with the Horizontal plane of the mass.

[@evgenytalantsev6995]

Perhaps it will be better to designate the angle for topple as beta, because other wise there is a confusion with two different angles each of those designates as alpha.

[@AutumnInsane123]

I seem to see a paradox... for the example with the pulley what happens when the object is in equilibrium? which equation will it take?

[@wubsyman5796]

how do you know that you dont instantanyasly adapt to the weight o the weel barrow?

[@monazza_]

This helped me a lot. Thanks

[@Aeghamedic]

Inertia, more massive objects are more reluctant to change their motion than less massive objects. A moving heavy object is harder to turn than a lighter one. A bowling ball is harder to get moving than a ping pong ball. Experiment: Have someone roll a bowling ball in front of you, left to right. Then, kick it and see what happens. Now, try it with a tennis ball. The tennis ball will likely move more off the original path than the bowling ball. Also, your foot will hurt less.

[@aditipatra6837]

Really effective!

[@colossalko]

This channel is about lectures to help people. The concepts are best explained by mathematics NOT magic or imagination. It's like trying to read a book in English without actually speaking English. You're basically asking for a translator. Learn to internalize math and you won't even have to concentrate that hard to follow along.

[@ischphil5965]

8:26 why is this alpha? is there a rule that says so?

[@paddyshanahanmathematics6918]

imgur.com/Gcj4HPX I made you a picture :) hope this explains it.

[@matthiash212]

Paddy Shanahan thanks for the drawing, if i understand right: you turned the triangle counterclockwise ?

[@DrPhysicsA]

You can show that the two triangles are similar so the angles are the same.

[@AlchemistOfNirnroot]

DrPhysicsA Oh, so that's why? I thought it was circle theorems lol

[@inda74f74]

DrPhysicsA Is X always facing the alpha ?

[@joshya812]

Do these videos apply for the A2 part of the Physics course?

[@shaikhpapi2083]

if we try to move something heave for example a T.V. from one room to another and if it doesnt move is this because of the friction force acting on it or because the object is heavy i.e have a heavy mass?

[@RuadhanG]

Assuming the object is on a surface and there isn't any obstructions, the reason it's not moving is because of the frictional force. It's not because the object is heavy, F=ma, therefore no matter how massive the object is and how small the force is (assuming it's greater than 0), the object will accelerate and therefore move, albeit a tiny amount. Now obviously the more massive the object, the greater the maximum frictional force and therefore the more force required to push it.

[@turicaederynmab5343]

Surely the more massive the object the more acceleration it would get and thus the less friction it would act against the object.

[@JackMitchinson]

Then make your own physics channel and do all of these extravagant things :)

[@zacharyt.johnson4285]

love your videos

[@omsaichowdharysuhakari1574]

got a clarity of basic terms used in friction

[@abadibi]

how do you know when to use sin, cos and tan?

[@coldstorage5036]

These videos are helping me a great deal in OCR Physics, thank you very much. Just out of interest, what is your background with physics e.g. school, university, A Levels etc...

[@DrPhysicsA]

cold storage Fairly normal. School then Uni - BSc and PhD.

[@tidomat1]

What would happen is the a/b were to equal mu(s), would it topple or would it slide?

[@DrPhysicsA]

It would be an unstable equilibrium.

[@BilalAhmed-fg7nl]

hello at the beginning of the video you said that if acceleration was 0 there would be no movement but surely if acceleration is 0 the object is still travelling at constant velocity (so still moving but at uniform velocity)?

[@DrPhysicsA]

Yes. If a=0 then according to Newton's first law the object continues in its state of rest or uniform motion.

[@StaticLinuxpro]

Wow this is harsh. I think he is a great teacher, even though I don't understand most of the stuff he is saying. No teacher can *bam* teach you physics in a day, week, or year. It's up to you as the student to make sure you pay attention, and actually be in class because you want to be in class.

[@JohnSmith-cy8hq]

Say you have a car. Say its normal contact force is 5000N and mu = 0.5. So the maximum friction which needs to be overcome by the engine force is 2500N for the car to start moving, right? But when it overcomes that force and starts speeding up the friction won't be constant. Friction force will increase with speed, engine force is constant so the resultant force will decrease until engine force = friction, a = 0 and car moves at constant velocity. My question is if this is true how is 2500N maximum force if it just reached for example 10000N which was the car's engine force forward? How does friction correlate with speed exactly, is there a formula or should we just accept that that's what happens for now at A - level? Thanks for your time

[@sandeep_aln]

The 'mu' referred in your query is the ‘coefficient of static friction’- whose identity is lost as soon as the vehicle overcomes the static friction and sets itself into motion. The net unbalanced force accelerates the car forward. Henceforth, the frictional force acting will be kinetic friction force ( the new ‘mu’ will be coefficient of kinetic friction).The two factors that affect the friction force between 2 objects are the normal force and the coefficient of friction be it kinetic or static. Kinetic friction does not depend on relative velocity of the surfaces usually. Part of the standard model of surface friction is the assumption that the frictional resistance force between two surfaces is independent of the velocity of relative movement. While this is approximately true for a wide range of low speeds, as the speed increases and air friction is encountered, it is found that the friction not only depends on the speed, but upon the square and sometimes higher powers of the speed. If there are fluid lubricants involved, then viscous resistance is encountered, and it is speed dependent.

[@JohnSmith-cy8hq]

Sandeep Aln Thanks for your response, I appreciate it. So the friction itself is constant but the engine force is constant and if you start at rest and hold the gas pedal at 70km/h you will accelerate until you reach that speed and then start to move with a constant 70km/h. The acceleration definitely decreases during this period, which means the net force decreases, and if the engine force is constant that would mean the resistive forces surely must be increasing. So is it the air resistance then that plays the big role here and friction is constant regardless of the increasing speed of the car?

[@sandeep_aln]

John Smith Once the car is set into motion, kinetic frictional force remains constant, irrespective of the speed of the car.So whatever friction force the car experiences during the accelerating phase is also constant.I found some useful info at - hyperphysics.phy-astr.gsu.edu/hbase/frict2.html. The graphs depicted may help us in understanding the nature of static and kinetic friction.

[@osdboza]

Great as always

[@mr8ty8]

hi love your channel and keep up the great work. Here is my question as friction has so far as we know a positive charge on objects with mass would it be considered an option that friction could arise on a massless object?lets say dark matter.we know anti matter is charged negativly.here is the idear im struggling with: whas the universe created by Dark matter and gravity that got centered so much that it created dark energy thru its friction and thus started to changed in to particles with mass due to being charged as positive instead of negative untill the density over came the pulling of its gravitational force and thus the universe began?

[@krishnanegikriss]

what is non-matter in this universe?

[@mr8ty8]

dark matter,dark energy,light itself and particles with zero mass

[@krishnanegikriss]

Nobody knows for sure.. One can't say that something is not matter just because it does not interact?

[@jayb1425]

Thank you so much

[@yiji0301]

You are the best

[@Smile_youreoncamera]

getting me through IB HL Physics

[@abadibi]

ayy! you too!

[@ritvikpandey8806]

Could you please explain kirchoff's laws a well. Especially their application thanks in advance

[@DrPhysicsA]

ritvik pandey Try kzbin.info/www/bejne/sIaop5Zvd9-nopo

[@lowgunuk]

Can I sample your voice in a dubstep track?

[@July-gj1st]

Why do you call weight force at the beginning ?

[@raspberries321]

+July17 Weight is a force. Weight = (mass)(acceleration due to gravity) = (m)(a) = Force

[@DrPhysicsA]

+July17 Weight is actually force. F=mg. Your weight would vary if you stood on the moon. But your mass remains constant.

[@anatollegros3454]

16:48 "remeber friction is always perverse"

[@agus3111]

All the forces lines must go through the c.o.g..as a condition

[@RupinderKaur-ob2xs]

nice ji

[@kosiokoye2384]

actually d bigger the object the harder it is to move (the greater the inertia) but u can say that law is not applicable in inclined planes... but still nice video

[@larsonwells2656]

Kosi Okoye wrong

[@kosiokoye2384]

Larson Wells how am I wrong... when u push a big or heavy object it is hard for it move because of its mass and d heavier or the bigger the mass d greater the inertia... pls explain What u mean by me being wrong

[@morganhill2909]

You are correct but this has nothing to do with the video considering this is basically the same question as "objects fall at the same rate due to gravity" If the object has more mass the force acting down the slope is bigger so friction is bigger thus cancelling it out as you say it isnt really relevant on inclined planes

[@walterdennisclark]

I guess you are right. Thanks for the insight. I will now go away with my tail between my legs.

[@ibrahimawadallah]

I suggest better lighting and better camera if you're planning on doing more videos.Thank you.

[@alsahliks]

thank you!

[@Jipzorowns]

thank you for this video's!

[@NiTZChavan]

THANK YOU... :)

[@aneelsubedi]

Its awsome

[@AlNoZaProductions]

Thank you!!!!! :D

[@farhadabedi8293]

thank you

[@Linshark]

It's not easy, it just seems easy :-)

[@bl4z3_kanazaki]

my kids will hear this :)

[@Cian389]

thanks!

[@Aeghamedic]

Not everything can be understood through simple examples. You need to understand the concepts which requires mathematics.

[@lalaywayn9990]

Thankyou

[@RupinderKaur-ob2xs]

please make new songs very nice

[@harisfrq]

i can hear you washing machine.. or you have some physicy type turbine...

[@jonathanlemuz9924]

😅😊❤

[@starview1]

360+1

[@austin04wf]

hey can you help me with this problem please your email address so i can send you the problem on wave functions

[@carterradke1414]

If you can't do math then your brain might be limiting you to learn physics...

[@stef9765]

hey u teach About some other chap

[@trafalgartorao9299]

i came from 2022

[@Shmarvv]

frickshin

[@itssaliceee]

my exam is tomorrow I think I want to die

[@DrPhysicsA]

Hope it went well.

[@YThursday]

Calm down, physics needs maths.......

[@ShankNBA]

Were you educated at Hogwarts? (sorry, immature, but I had too lol)

[@ShankNBA]

But you're a great teacher, thank you!

[@098josh098]

I dont think he was thats a movie lol

[@walterdennisclark]

Revision? Is there something in the least bit revolutionary about your approach? No. Same ol' boring math stuff with no exciting examples. How about a video of the test of airplaner brakes. Or the way thy install turbine blades with spinning the components until they are red hot. You, like ALL PHYSICS INSTRUCTORS ARE LIMITING PHYSICS TO ONLY THOSE WHO CAN DO MATH BETTER THAN ANYONE ELSE. THAT IS THE ONLY APPEAL YOU CREATE.

[@bishankagrawal2948]

thank you