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A metal coin of mass 5 g and radius 1 cm...

A metal coin of mass 5 g and radius 1 cm is fixed to a think stick AB of negligible mass as shown in the figure. The system is initially at rest. The constant torque, that will make the system rotate about AB at 25 rotations per second in 5 s, is close to:

A

`1.6xx10^(-5)Nm`

B

`2.0xx10^(-5)Nm`

C

`4.0xx10^(-6)Nm`

D

`7.9xx10^(-6)Nm`

Text Solution

Verified by Experts

The correct Answer is:
B
`tau=Ialpha=(5)/(4)mR^(2)alpha`
`alpha=(4tau)/(5mR^(2))`
`omega=2pif=omega_(1)t+alphat`
`implies2pixx25=0+(4tauxx5)/(5xx5xx10^(-7))`
`tau=(25xxpixx10^(-6))//4=1.962xx10^(-5)Nm~~2xx10^(-5)Nm`.
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