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Mechanics

Hot goIITian

Joined:	7 Aug 2007
Post:	184

1 Apr 2008 22:36:57 IST

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504

rotation:fiitjee aits question...

None

a string is wrapped around a cylinder of mass M and radius R.the string is pulled vertically upward to prevent the centre of mass from falling as the cylinder unwounds the string.find the length of the string unwound by the cylinder when the speed of the cylinder is

answer:

)² / 4g

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Comments (3)

Anup

Hot goIITian

Joined: 9 Nov 2006

Posts: 127

1 Apr 2008 22:47:35 IST

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i'm gettin it as Rw^2/4g

my method...........

TR=Ia (a= angular accelaration)

since C.M is not falling T=Mg

MgR=Ia...............I=MR^2/2

a=2g/R

w^2=2*2g/R*s ..............s=Rw^2/4g

Rahul Sharma

Scorching goIITian

Joined: 29 Aug 2007

Posts: 222

1 Apr 2008 23:02:00 IST

Like 2 people liked this

Anup, thats the angle it will rotate. To get the length, you have to multiply by R and thus you'll get the answer.

Anup

Hot goIITian

Joined: 9 Nov 2006

Posts: 127

1 Apr 2008 23:05:38 IST

Like 0 people liked this

ya thanx for dat........it completely slipped out of my mind that its the angle......

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