1when going up , the point of contact tends to move down , so friction acts up , and while moving down, the point of contact haas atendency to move up , so friction has an upward direction.
a sphere is rolling up an inclinced plane.....
and thn returns rolling...
wot is the direction of friction in both the cases??????????
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24 Answers
11wen it rolls downwords friction acts in the downword direction.if it is a wheel or spherical object frictn acts in the dirn of motion if any clarification pls respond....will surely make ur doubt crystal clear
1Again i think in upward direction........and as fr the diagram I hav assumed it while d sphere is going upwards
1now take another case,,,
if i initially give an angular velocity w in anticlockwise direction (as in your fig) and keep it on the incline plane??
then think.... wat should be the direction of friction...
62Does rolling imply Pure Rolling?
If it does.. ur answre is correct Namika!
1
The friction is acting in upward directionbecoz we hav to satisfy the condition v=rw(omega)..........fr rolling motion.......becozwhile going upwards velocity is reduced hence d omega is increased...to reduce it and to satisfy d above condition Frictoin should act upwards
1noooooooooooo :(
read all the posts writtn above... u willl know whr u are wrong....
1both cases upward......coz wen goin up..it has tendencey to slip down n when goin down..same thing............
1arey... why dont you post a question????
we will try to solve n then u will get an idea how to proceed with such kind of questons......
post a particular question/
62or angular acceleration! i mean where do u know that there is no angular velocity.!!!
62hmm.. it is insufficient to say!
One justification: is it possible to say the direction of friction when a sphere rolls on a plane surface??
Even on an inclined plane, you need to knwo v, r and ω! (eg front wheel back wheel of a cycle!)
We see the relative motion of the point of contact! that is where we decide.. always! Friction opposes relative motion!
1friction will be upwards in both cases because we have the component of the gravitational force?(i.e.mgsin theta acting downwards)...Assuming that it is not slipping throughout....the angular acc will not change(i mean ...it will be same for both cases)...
1very tough i think.. i cant get it exactly.. but some idea i have got...
62no.
i will give u a case...
start with a plane.. (zero incline..) then think...
1but i think that the question is in which direction the friction will act
so i think that there is no need of angular velocity in the question
since it is on inclined plane
and the friction acting on the ball is static
62No shalav that is nto the right answer...
we know nothing about the angular velocity (ω)
So nothing can be said...
1since friction always opposes the relative motion or opposes if there is a
tendency of relative motion in both the cases the tendency of ball is to
go downward so the friction acts up the plane
62a sphere is rolling up an inclinced plane.....
and thn returns rolling...
Even i missed out this "and then"
Btw i was nto trying to say that ur solution is wrong.. u did the same mistake that i made last night.. jumped to a solutin without reading the question correctly :)
Your Concept is perfectly correct!
1ok but that we can say only when we have a prob at hand naa?
i jus told a general case......
62This is not the complete solution..
This is a very very tricky problem...
Basically the part when the ball starts to roll back... downwards.. how do u prove that it is indeterminate...
I mean the velocity will be -ve.. we need to prove(or show by example)
that indeed there can be values of ω for both directions...
Tricky, confusing.. but doable...
1if rolling is faster than translation, then ωr>v, sliding at the point of contact is backward so friction direction is forward.
if the case is ulta,,,, friction direction ulta....
