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A bullet of mass 10 g moving horizontall...

A bullet of mass 10 g moving horizontally with a velocity of `400ms^(-1)` strikes a wooden block of mass 2kg which is suspended by a light inextensible string of length 5 m. As a result, the centre of gravity of the block is found to rise a vertical distance of 10 cm. The speed of the bullet after it emerges out horizontally from the block will be

A

120 `ms^(-1)`

B

160 `ms^(-1)`

C

100 `ms^(-1)`

D

80 `ms^(-1)`

Text Solution

Verified by Experts

The correct Answer is:
A

AB=5

Apply conservation of linear momentum
`mu+0=mv+MV`
`(10)/(1000)xx400+0=(10)/(1000)v+2V`
`0.01v+2V=4` …..(1)
PE=KE
MgH=`1/2xxMV^2`
`2xx10xx(10)/(100)=1/2xx2xxV^2`
`implies V^2=2`
V=`sqrt2ms^(-1)`
Substituting the value of V in Eq. (1), we get
`(v)/(100)+2sqrt2=4impliesv=(4-2sqrt2)100`
=120 `ms^(-1)`
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Knowledge Check

  • A bullet of mass 10g moving horizontally with a velocity of 400 ms^(-1) strickes a wooden block of mass 2 kg which is suspended by a light inextensible string of length 5m . As a result, the center ofgravity of the block is found to rise a vertical distance of 10cm . The speed of the bullet after it emerges out hirizontally from the block will be

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    `120 ms^(-1)`
    B
    `160 ms^(-1)`
    C
    `100 ms^(-1)`
    D
    `80 ms^(-1)`
  • A bullet of mass 10 g moving horizontally with a velocity of 400 ms^(-1) strikes a wook block of mass 2 kg which is suspended by light inextensible string of length 5 m. As a result, the centre of gravity of the block found to rise a vertical distance of 10 cm. The speed of the bullet after it emerges out horizontally from the block will be

    A
    `100 ms^(-1)`
    B
    `80 ms^(-1)`
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    D
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