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The bob of a pendulum of length 2 m lies...

The bob of a pendulum of length 2 m lies at P. When it reaches Q it loses 10% of its total energy due to air resistance. For this event, which of the following is a correct statement.

A

The velocity at Q is `1m//s`

B

The velocity at Q is `6m//s`

C

The acceleration at Q is `3m//s^(2)`

D

The acceleration at Q is `6m//s^(2)`

Text Solution

Verified by Experts

The correct Answer is:
B
`K.E=(1)/(2)mv^(2),P.E.=mgh`
K.E. at Q = 90% of P.E. at P
`(1)/(2)mv^(2)=(90)/(100)mgh`
`v^(2)=0.9ghxx2`
`v=sqrt(1.8gh)`
Here `g=10m//s^(2) h=2`
`therefore` Velocity at `Q,v=sqrt(1.8xx10xx2)=sqrt(36)=6m//s`
The other statements are incorrect.
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