IIT JEE , AIEEE Forum - Physics , Mechanics

ninadroxxx

plz can ne1 explain abt rolling and the difference b/w rolling nd sliding

I have a doubt wht is rolling friction and it is a misnomer is it true and plz explain abt the direction of frictional force as to where it acts a body is rolling

paddy.dude

in rolling there is translational as well as rotational motion......but in sliding there is only translational motion

i dont know bout rolling friction but is there such a thng.........i know that a minum coeficient of frcition must be needed for pure rolling .........

ninadroxxx

plz check whether i m correct is rolling friction the horizontal component of normal force and it depends on the hardness of the body plz explain wht role does rolling friction play
How to find the direction of friction 4 a rolling body

akshay.khare91

Yes, in case of pure rolling the force of friction acts
Let us consider a example
IF a body is rolled and placed on a surface with friction and also we have given
it a velocity then if V> then friction force acts in backward direction to
provide it a torque and increases it angular velocity so that v=r.
And if V< then friction force acts in forward direction to reduce angular velocity
so that again v= r...

and if we are performing the above experiment on a inclined plane so that
Mg has two components Mgsin and Mgcos .Since Mgcos is balanced
by normal reaction and it has no torque. Also Mgsin has no torque
therefore there is only frictional force which will provide a torque and
will cause pure rolling v=r

however work done by frictional force is zero

I DONOT FOLLOW THE RULES I MAKE THEM TO FOLLOW ME.

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28 Mar 2008 16:21:46 IST

Subject: rotational conceptual doubt

ninadroxxx (21)

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is it necessary tht work done by friction in rolling is 0 in pure rolling it is zero

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29 Mar 2008 00:39:22 IST

Subject: Re:rotational conceptual doubt

tachyon_c (0)

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look net work done by the friction is zero in case of accelerated pure rolling,two things,translational work due to friction and rotational work due to friction add up to zero

for e.g if friction acts backward with c.o.m translating forward,it does negative work corresponding to translation and the torque due to friction does positive work and the net becomes zero

_{[ ]}

^{[F.ds -FRd ]}

=0 since v=r w or ds = rd

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