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A carpet of mass m made of inextensible ...

A carpet of mass m made of inextensible material is rolled along its length in the form of a cylinder of radius r and kept on a rough floor. The decrease in the potential energy of the system, when the carpet is unrolled to a radius `(r)/(2)` without sliding is (g =acceleration due to gravity)

A

`(3)/(4) mgr`

B

`(5)/(8) mgr`

C

`(7)/(8) mgr`

D

`(1)/(2) mgr`

Text Solution

Verified by Experts

The correct Answer is:
C

Mass left over unrolled `= (m)/(pi r^(2)) xx pi ((r)/(2))^(2)= (m)/(4)`
decrease in P.E. `= mgr- ((m)/(4))g (r)/(2)= (7)/(8) mgr`
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