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A body is released from height of 30 m v...

A body is released from height of 30 m vertically downwards. The speed of the body at which potential is twice that of kinetic energy is
(Acceleration due to gravity , `g = 10 ms^(-2)`)

A

`20 sqrt(20 )ms^(-1)`

B

`10 sqrt(2) ms^(-1)`

C

`10ms^(-1)`

D

`20 ms^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
B
Total energy at heigh 30 m = mg (30)= 30 mg
`:. TE = PE + KE rArr 30 mg = PE +KE . . . (i)`
From Eq. (i),
`rArr 30 mg = 2KE +KE`
`rArr KE = 10mg rArr(1)/(2) mv^(2) = 10 mg`
Hence, speed of the body , `v = sqrt(200) = 10 sqrt(2) ms^(-1)`
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