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The bob of a pendulum is released from a...

The bob of a pendulum is released from a horizontal position. If the length of pendulum is 2 m, what is the speed with which the bob arrives at the lower most point. Assume that 10% of its energy is dissipated against air resistance.
(Take `g = 10 m s^(-2)`)

A

`4 m s^(-1)`

B

`6 m s^(-1)`

C

`8 m s^(-1)`

D

`10 m s^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
B
The situation is as shown in figure
Potential energy of the bob at A =mgh
Kinetic energy of the bob at B =`1/2 mv^2`
As 10% of the energy of the bob is dissipated against air resistance.
`therefore 1/2mv^2=90/100 "of mgh or"v^2=2xx90/100xxgxxh`
`v=sqrt((2xx90xxgxxh)/100)=sqrt((2xx90xx10xx2)/100)=6 m s^(-1)`
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