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A disc – like reel with massless thread ...

A disc – like reel with massless thread unwinds itself while falling vertically downwards. The acceleration of its fall is:

A

Zero

B

g

C

`(2g)/3`

D

`g/2`

Text Solution

Verified by Experts

The correct Answer is:
C
Let us consider the instant the reel has desceded distance h Loos of PE =Translational KE + Rotational KE
`:.mgh=(1)/(2)mv^(2)+(1)/(2)Iomega^(2)`
`mgh=(1)/(2)mv^(2)+(1)/(2)((1)/(2)mr^(2))(v^(2))/(r^(2))`
`gh=(3)/(4)v^(2)" "," "v^(2)=(4)/(3)gh`
`v^(2)=2ah," "(4)/(3)gh=2ah," "a=(2g)/(3)`
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