Physics Lesson: Pulley Problem w/Friction Part 2 for high school

[abhikch1992]

how can the 5kg block pull the 6 kg block down????

[deniseshabbychic]

what if the mass of the object in the surface is 100N and the object hanging is 50N, will it still go down? thanks

[RobertoEmilioRomero]

The Tension should be 30.7364 Newtons, and the Acceleration 0. Since mass on surface is greater than the mass that is suspended. The only way mass of 5kg can accelerate down is if energy in this system is created, which is impossible.

[RobertoEmilioRomero]

Why will the mass of 5kg accelerate down if the mass on the surface is greater.

[Beaztmaster]

thanks alot!

:)

[m1llernigga]

thanks!

[PhysicsEH]

@m1llernigga Glad to help.

[vb4des]

new you can upload 15 min in youtube

take your time..:)

thanks..

[TeaBubblez]

shoudlnt Fg be = m*-9.8? why do u continuously use 9.8

[PhysicsEH]

@TeaBubblez The sign on the 9.8 depends on what sign convention you choose. I chose to make the direction of acceleration = (+) so for the 5 kg the 9.8 is down and down is (+) so it's +9.8 For the 6kg the Fg was not even in the direction of the acceleration, had no effect on the acceleration and I was only looking for its magnitude so that I could calculate the Ff so I used +9.8. Many people choose up as positive for problems and so 9.8 is (-) but you can choose either sign convention.

[MyZeyar]

@PhysicsEH good explanation

[StackinnBuddah]

real nicee

[PhysicsEH]

@StackinnBuddah Thanks. Glad to help.

[fuddyism]

Oh yeah, the first post here talks about the Ff, should that number actually be 8.8N in your x-direction equation?

[fuddyism]

I don't understand how you got 40.2=11a. I f you're adding the equations together, shouldn't that number turn out to be -9.8? Please explain

[InterplayDesigns]

you made the company lg come true

[glupoi652]

as a student of GSMST, this really does help me understand this concept more in depth, as I did this a long time ago, and I completely forgot this topic... thank you so much.

[PhysicsEH]

@glupoi652 I'm glad our videos were some help.

[ThreeEscapeas]

Are you really allowed to add the two tension equations eventhough one is in the x-direction and the other is in the y-direction? Why can you?

[PhysicsEH]

@ThreeEscapeas Hi. You can add the 2 equations because we set the direction of acceleration as the positive direction which allows us to do this. This means that the 2 directions are treated the same for the purpose of calculations. The forces involved also affect both of them causing the same acceleration so we can treat it as one continuous rope. I hope this helps because it's not an easy question to answer.

[ThreeEscapeas]

@PhysicsEH Alright thank you! I think I understand it.

[14bdl]

you guyyss are awesomee(Y)

its really helpfull!

thanks so muchh:)

[PhysicsEH]

@14bdl Thanks! Glad to help.

[PhysicsEH]

Thanks for the feedback. Glad to help.

[emilyh12345]

I should have studied and done my homework before youtubing the night before my exam haha :)

But this helps so much more than trying to make sense of my textbook, THANK YOU! I like how you explain the concepts and not just plug in random equations

[redbuffalo75]

this is better than my physics teacher....

[wakeskata]

you are a lifesaver two days before final exams!

[ltan11]

i wish my teacher did this

[gavmack11]

i think i can do this now...thanks

[PhysicsEH]

AAAARRRRGG! You are right, I should have used the 8.8N. I'll try and replace this one next time we make videos. Good work there rollercoastermike, and thanks for the kind words.

Mark

[rollercoastermike]

thank you so much for your series of videos--i'm finally understanding FBDs and tension!

one thing: i believe you meant to insert 8.8N for your friction force at 4:58, so the step at 6:45 doesn't make sense. i think that also changes the tension that you end up with.