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Two discs A and B touch each other as in...

Two discs `A` and `B` touch each other as in figure. A rope tightly wound on `A` is pulled down at `2m//s^(2)`. Find the friction force between `A` and `B` if slipping is absent.
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Text Solution

Verified by Experts

The correct Answer is:
`2 N`
`a_(t) = R alpha`
For `A 2 = ( R) alpha_(A)` (given) …(1)
At point ofcontact no slippling take place
:. `R omega_(A) 2 R omega_(B)`
differenciating the equation with respect to time
`alpha_(A) = 2 alpha_(B)` ….(2)

`(2)/( R) = 2 alpha_(B)` & `alpha_(B) = (1)/( R)` ...(3)
For `B 2R xx f = I alpha`
`f xx 2R = (1)/(2) xx 2(2R)^(2) alpha_(B)`
`f xx 2R = 4R^(2) xx (1)/( R) rArr f = 2 N`.
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