Friction & Newton's Laws Part 7 Stacked Blocks FBD Physics

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Key Words: Newton 1st first and 2nd second law dynamics mechanics free body diagrams physics lesson help coefficient of friction ropes pulling on boxes fbd

[@ariasaremi2983]

In part b, shouldn't the friction force applied to the top of the 5kg block be dynamic friction since the 2kg block is moving?

[@adamradekmartinez1536]

I was thinking the same thing. Now since the force is > 6.86 the u he used is no longer valid.

[@robinraj4812]

Since it already exceeded 6.86 N...so no longer used..

[@ngd5564]

thanks a lot i broke a barrier in understanding these problems here.

[@Andy-mo7ol]

Why is the frictional force still taken into account for part B if the block, on top, slips off immediately. Is it correct to assume that the answer for part B is perhaps only the initial acceleration, in that one moment that the upper block is still on the bottom block. After x amount of time, the top block will slide off and the object will increase in acceleration.

[@aniruddhvasishta8334]

I know I'm a year late, but I think the friction in that case would be the force of kinetic friction, which is always less than the force of static friction. As soon as it slips off though, the force will no longer apply.

[@spoopspoops5328]

god bless you my brother. you are real one

[@williammo3581]

You are my LIFESAVER, THANK YOU SOO MUCH

[@MegaAwsomegirl101]

Thanks a lot! I had a similar problem and this video helped me very much :)

[@CamillevanderWatt1]

one of the best physics videos I've found!! Thank u so much!

[@aodenteo6855]

Why did he take the value for friction in part be to be 1.96? Shouldn't you have to take friction between the 2 blocks to be kinetic friction since the top block is moving with respect to the bottom block? In which case is part b) even possible to do without knowing the coefficient of kinetic friction between the 2 blocks? I apologise in advance for any stupid mistake that I may have made.

[@DanHartwigMusic]

For part b) Wouldn't the kinetic frictional coefficient be less than the maximum static frictional coefficient once it starts sliding? I know it isn't given, but realistically?

[@namankarn1504]

You're right it would be so...but unless stated we take the value of Kinetic friction to be equal to that of Static friction...

[@leorio7416]

that's exactly what I thought

[@momowmoh]

you didnt account for the friction force acting in the opposite direction for Fa

[@colly9888]

thank you so much mr physicshelp canada

[@Couldyanot]

so helpful, your manner or explanation is amazing, well done!

[@steve4718]

cuz he's canadian??

[@theonlyashleybrooks1]

Is there any way you can do complex time dilation problems in detail.

[@sakureema9899]

we know that the kinetic friction is always less than the maximum static fricion (Fsmax> fk) and so i think you should not use the Fsmax from part a in part b. the second part (b) can't be solved unless we know the coefficient of kinetic friction so we use the correct fk for the lower block! am I right or wrong!?

[@suchitakanala2392]

static friction is greater than kinetic friction

[@karanchampaneri1690]

So what would you do to solve a question with multiple boxes stacked on each other?

[@huka6965]

ECE 105

[@marinoraven9598]

What if there WAS a frictional coefficient between lower box and the ground?

[@TheHiddenChronicle-b9l]

then you cant solve it

[@sachinmalik5837]

deserve .many likes

[@trinitywr6347]

I exam tomorrow and I’ll come back to thank you if I don’t forget your teaching during the exam

[@marcusbluestone2822]

Super awesome explanation - thank you!!!!!!

[@pahul79]

thank you very much, very appriciated

[@Asdbcrewqopijcklxzn]

How did you know that the acceleration you calculated was the max and not the min?

[@vivvpprof]

Why is friction pushing the top object to the right?

[@namankarn1504]

It is wrong notion that 'Friction opposes motion' actually... 'Friction opposes Relative motion' between two objects..as it does in the above case and in turn pushes the object to the right... #hopeUgetIt

[@rango9404]

Naman Karn
I don't get it

[@namankarn1504]

Consider the bottom block..it is moving towards right...Now, if you look at the upper block from the reference frame of the lower block, it appears to slide towards left (that's bcoz of inertia of rest) ..So as I said the friction acts in a direction so as to nullify or reduce the relative sliding between those two.....& as u might have guessed by now it acts towards right (opposite to the relative sliding).......Think over it!!!

[@rango9404]

Naman Karn
Ahhh that helped a lot! Thanks for clearing it!

[@namankarn1504]

:)

[@selifiaib1657]

Really thank you, I now understand why I didn’t do well in My exam

[@yalimeydad5253]

such great explanation! thanks!

[@eitang7086]

excellent explanation

[@TheHiddenChronicle-b9l]

thank you so much such a helpful video!

[@pauljburgess7423]

Thank you SO MUCH for this.

[@catlord69]

thank you

[@jessicazhang6508]

thanks