Work/Energy problem with Friction

[owaisoz]

u just need that pen that writes on the screen to accomplish the perfectness of teaching physics online, (+a calculator in all vids :P) , other than that ur (y)

[theshark747]

Thanks

[Zumerjud]

energy IS conserved its just converted into heat, that iswhy you don't get the total KE equal to PE at the beginning. you should've stressed on that

[DaBojangler]

isn't Wf equal to F∆rcosø? because W=F•r which is a dot product...

[adamaqmal]

These video make my understanding better

[ArunSrinivasa]

Dear Mr. Khan

Please stop doing Physics explanations. Indeed, energy is ALWAYS conserved. For this problem should talk only about Mechanical energy or kinetic energy. This idea of ''energy wasted by friction'' etc is not correct. The answer is correct but the explanation is wrong, You are a great explainer ,but if you provide misleading explanations, we professors in engineering have to spend a vast amount of time correcting these misconceptions with only limited success. Prof Arun Srinivasa

[TheRick309]

I'm a little confused what was the point of having the incline? Was it simply to get the height? I figured since you had an angle you would use, work = (force * cos theta) * d? Why didn't it apply here?

[TaraLynn218]

@TheRick309

friction?

[jack390]

our physics teacher doesnt explain that well, so we just play psp in class but thanks to you i understand all of it!! :D

[oluwashehunaina]

am feeling you sir hear in nigeria,r u  a professor of physo

[stiffz]

Isn't it easier if you used the work/energy relationship instead?

by that I mean:

total work = difference in kinetic energy.

where in that case, you calculate work done by friction, you calculate work done by gravity, you subtract them to find your total work, and you equate your answer to 1/2.m.v^2 to find your final velocity.

Maybe it's just a matter of preference, but good job!

[gratitudeforall]

@stiffz thanks your way is quicker in exam! However I agree this video is helpful and helped me understand!

[plasmaluz]

You are great at physics, thanks. Here's my two cents: the Windows' calculator has a scientific mode with trig buttons in the view menu.

[loik345]

U r awesome man. Good explanation.

[akhockey77]

Wanted to say you saved me from failing my midterm! Thanks a lot keep it up

[Joseph1396]

THESE VIDEOS MADE ME COLOURBLIND FOR 5 MINS AFTER I SPENT 30 MINS OF WATCHING THEM... CANT SAY THEY ARENT HELPFUL BUT COLOURS ARE REALLY IRRITATING ... Hes got 2,000 videos so he cant just change them but next time try to tace care about things like these...

[bhahmz]

You SIR are AMAZING! I'm doing 12 A2 exams in January - 5 of which I need to teach myself! :(

I've always not liked doing M2 since I don't understand the textbook and I don't like bugging my teacher for help all the time. But now that I've found your videos, I'm finding mechanics more and MORE enjoyable! :)

Thank YOU! :)

[Oneill9293]

@bhahmz 12? Shit, I'm bricking doing only 7 haha. Best of luck pal.

[bhahmz]

@Oneill9293 haha oh well, I was the one who signed up for it - thinking anything's possible as long as you put ur mind to it. xP And still believing! hehe :) Best of luck to u too m8.

[bisharalol]

2 people are just as dumb as justin beirber.

[281MeXiCaN713]

i hope your gettin paid alot for these videos, because i learn more from you than from my teacher

[snarper]

THX! You just saved my sorry ass

[SmokerTJ]

man this guy SOO much better than my physics teacher...my teacher is so tedious, repetitious, redundant and monotonic in nature and teaching style. AND the worst part is you dont get it so you end up losing interest and getting bored to sleep, i mean this guy explained it in 10 FREAKIN minutes! whereas my teacher can spend three hours and i dont get it!

[slnj25]

I love you so Much THANK YOU!!@!!@!@@ !!@!@!

[MsRoseapple]

Thank you very much.understood than former:)

[CrimsonSoul777]

Hahaha Slide down a slide of sandpaper... HOT PANTS!

[Cryptically]

if the guy pedaled down, you would add kinetic energy to the potential energy right?

[ubercute1sf]

@Cryptically only if its constant. and its not constant because the guy will continously pedal making him go faster.You should multiply his acceleration with the mass and then multiply with the distance. This value can be added just like the friction was taken away. or add his acceleration and the acceleration of gravity from the begining it would make it alot easier.

[kennetchieful]

how does it became 38.5 KJ..why did you convert that..instead of joules?..tnx ^^,

[Taowhr]

@kennetchieful he ran out of spaces.

[tamerthelame]

thank you soo much you were a huge help :)

[dsoviravong]

It makes a lot more sense to me now that everything's explained step-by-step. Physics is so interesting, but still so frustrating to me because the concepts always seem so hard for me to grasp. I'm watching a bunch of your videos and they're helping tremendously. Thanks again!

[PeaceFighter2]

if it is given only the coefficient of friction how can we find the friction force??

[nomania]

my physics teacher's 70 or something years old who deserves to die. thanks so much for your videos, i get it now

[tngbm]

I'd like to point out that since it's a bike (with wheels) the friction is not tire to ground. With wheels friction is in the same direction as motion.

In this case I guess it would be the brakes like you mentioned.

[sharikokaine176]

@tngbm Yes but the ground isn't moving with the wheels.

Example: Try stroking your right hand(Wheels) on to your left hand(ground) when your left hand(ground) is not moving. There is still some heat right? because the wheels are moving when there is intertia from the ground too. This creates the friction.

[onlyAerik]

he keeps SAYING the website, but how do you actually write it out?! zeeboo?  zboo? zebu?

[lumaix]

@onlyAerik zebu.uoregon.edu

[DeflocculatedDentist]

sandpaper slides have got to be one of the most sadistic things i've ever heard ;)

[DeflocculatedDentist]

the calculator on my computer gave me 43.5

[berberda]

its because he is finding the negative work. The negative work is force time distance. This is why he does -60N * 500m because that is the negative work that the force of friction does.

[stealinglemons]

around 7:30 why is the force of friction, Force * distance. 60N*500m maybe I'm forgetting something hear.. please reply!

[DartmouthAlum96]

I really like how you set this up using PE and KE. It should also be pointed out that the question can be solved by determining the components of Force Weight when the bicyclist is at the top of the hill, the subtracting the work done by friction from the work done by the Force Weight Parallel. This gives you total work, which is the same as KE. Then you can use your KE formula and go from there to calculate the velocity.

[ITyrantl]

OMG! thank you so much!! my teacher makes everything seem so complex... idk whats wrong with him. he explains it so wierd...<3

[wahkimoocow]

thank you soo soo soo much!

[Whatsthedealwithit]

your videos are amazing our physics teacher isnt the greatest but she tries .. she admits your videos are better and uses them all the time to help us understand concepts thanks for sharing your knowledge

[azngirlchibi]

OHHHH, I get it now! Thanks so much - this is a big help, and you explain so much clearer than my physics teacher!

[traidatnay99]

i agree most of the teacher in school is only good at dump us down. They are trained to do that. so sad.

[Legalios]

When determining the work done by friccion your calculations are incorrect since you are supposed to include the Angle at which the object is falling hence (-Mu*Mass*gravity*distance(cos­ine(5))

[magicOcardOman2009]

lol wat r u talkin about, when he gives u force of friction, FORCE OF FRICTION, it already includes the angle, ff=uFN, FN=mgcos(angle), he has ff, so u dont care about including the angle anymore its already been used to find Ff.

[amrit2232]

GREAT BASIC CONCEPTS

[iamsiau]

Thx! lots f help. This is like getting an educationl for free. :)

[abhinav777]

that is the whole point of his website! :D

[obsdj]

This, to some degree, is a potential energy problem, it definitely is a potential....huh huh huh.... a mechanical.... law of.... it's definitely a conservation of mechanical energy problem...

lol

Nice video man!

[battlefort501st]

Thanks man =D

[laurence00vii]

you are my heroe!

[studtulloss45]

HAHAHA clicking through each video in 2 sec. intervals: "welcome back", "welcome back", welcome back", welcome back", ......

[xlwaiyiplx]

stop it!

[Duckalore]

i dont like that colour

[sjb167]

I don't like how you spelled color with a u

[megaelliott]

go england!

[otuonyec]

well the first spelling of colour when it was derived from latin to english was COLOUR.........The Americans, being oh so great *sarcasm* >.> changed not only that to "color" but also other words to suit them........I take it your american. >.>

[sjb167]

lol yee, we just spelled the word how it sounded, which is how words should be spelled

[otuonyec]

yea thats what all americans i've said that to say lol..u've got like 6 dislikes because of that comment....

[MUsnaredrummer]

I'm glad you can see that Americans are great.... because we are...

[m1dnightshadow]

thanks a lot for thisw mann :p appreciate it! .. all your videos

[SilurianZ]

Hey Sal, u can do trig functions on windows calculator...select scientific in the 'View' menu. thx for the vid!

[soepaygyi]

Excellent explanation, and very helpful. Thank u so much 4 that, Jeff. I would like to request this kind of Conservation Energy problem with coefficient, like ice plane to sandpaper.

[emmanuelfaluade]

Wouldn't the friction be the same direction of the motion because the relative motion of the tires on the bike are moving in the opposite direction of motion so the frictional force oppose that motion. Meaning that the frictional force is moving down the hill!!!!

[sistematico17]

thanks once again sal! keep doing this :D

[waterserpent1412]

the math is wrong... but it's good review

[TBRESS]

Great Videos!!! They have helped me study for physics and calculus a lot... What program are you using for the demonstrations?

[bj24563]

Thanks so much for these awesome videos! They make a great test review for AP Physics BC

[hartj558]

I am taking Physics for the first time through a distance course and I find these videos not only interesting but very helpful!!

Thanks for taking the time

Jeff

[idricool]

I like your videos. I've learned a lot.