Physics Lesson: Pulley on a Ramp Problem (Advanced) for high school

[azharmohammed0]

BOO!!!! you suck lol

[xxxEnChantedxxx]

Why will acceleration (a) end up being zero? Do we conclude that it's stationary because friction > acceleration?

Thanks so much!

[PhysicsEH]

@xxxEnChantedxxx The friction formula calculates the maximum friction available. If you pull an object with 4N and you calculate the friction as 5N then you actualy only get 4N of friction since that is all that is required and the object will stay at rest. In this example the maximum friction was more than required so there was more than enough to keep it at rest so the accel = zero. That is, the max friction is larger than the total force pulling it to move. i hope this helps.

[matiarjafari]

@PhysicsEH so im confused as to what keeps the system staitionary rather than going down the ramp? in other words why doesn't the 5kg body on the incline slide down pulling the 3kg body?

[Zeraan1337]

How can you just cancel the tension and put 3(9.8) in for it?

[mytkt93]

THANK YOU = ). It helps me a lot.

I have another question, why the system will not start when the acceleration calculated is negative? Negative acceleration means the 5kg object remains stationary or moves down the hill? My problem is that I don't understand what is the negative accel stands for. Thank You

[PhysicsEH]

@mytkt93 When you start this type of question you need to guess which way it will accel. If you guess right, the accel is positive. If you guess wrong, it ends up negative. If it ends up negative you can't just say the accel is the other way because the calculation is wrong. You need to start the question again assuming it will accel the other way and the free body diagram will end up different (the Ff would be the other way) As a result the accel will be a different magnitude. Hope this helps.

[mytkt93]

if the acceleration of the object is negative, how can I explain the situation of the system in order to say that the system will not start.? Thank you. = )

[PhysicsEH]

@mytkt93 Hi. If the system does not start then the forces in the x-direction on each mass is balanced so on the 5kg the equation becomes Ft - Fgx - Ff = 0 and not "ma" since the acceleration is zero. You can now figure out Ft since you can find Fgx and Ff. The easier way is to look at the 3 kg object. The equation for this is Fg - Ft = 0 since the accel is zero, so Fa = Fg or 3*9.8. When the sytem does not move the question is much easier. I hope this helps.

[ipodvidoe]

Wow, great job! 

[PhysicsEH]

@ipodvidoe Thanks. glad to help.

[MrIntelligenius]

"and now your confused lmao"

[krazykrutz00]

you remind of that genius guy from "the hangover"!!

[sukhy28]

You magnificent bearded man

[treblajf4]

Hey this helps out so much please keep them coming. But i had a Question. What if the masses were equal in this problem. And does the angle affect if the system will or will not move??

[ljohnbird]

@treblajf4 If the masses are equal: instead of a=(29.4 - 18.5 - 8.5), it will be a=(49 - 18.5 - 8.5) so there will absolutely be movement lifting the weight up the ramp.

The angle does matter for this problem. The larger the slope the less friction, but the greater the force gravity applies directly to the object (fgx). Imagine the ultimate slope - 90 degrees. There would be no friction, but 100% of the force of gravity would pull the object downwards.

[PhysicsEH]

@treblajf4 If the masses were equal it still might move down the hill in the same direction because all of the gravity on the right mass is pulling the system and only a component of the left mass is pulling in the opposite direction. The angle will also make a difference. The angle effects the size of the component of gravity that is pulling the left mass down the hill. The larger the angle the larger the component of gravity so it is more likely to move down the hill or not at all.

[treblajf4]

@PhysicsEH thanks this really helps alot :)

[MellowCruisin]

This guy is a really good teacher.

[PhysicsEH]

@MellowCruisin Thanks for the comment. Glad to help.

[PhysicsEH]

@jgill303 Hi. Thanks , that comment made my day and is one of the nicest we have gotten. Glad to help.

[TheEirica]

i love how you guys TEACH! like you actually TEACH! my proffessor is smart, but i dont get his explanations...now im going to cram all of your vids, i dont think i've ever opened my book again after watching your videos

[lovvinhim]

THANK YOU!!!

[2much2teach]

Im so grateful for you guys, thanks

[Av3rnus]

Thanks so much for these videos they are so helpful and you are really making a huge difference in world, in the positive x direction :).

[Wilshier]

I LOVE YOU GUYS SO MUCH RIGHT NOW!!

I was finally able to solve the problem ive been working on all day. thanks again.

[PhysicsEH]

Wow, Thanks! We are going to try and make some more in the next few days.

[shei5tko0om]

thanks alot :)

[bellanei]

Thank you

[Sungtaek]

this will probably save my life tomorrow. thank you!

[mdodso00]

its just simple physics...