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A frequently used device to measure the speed of bullets is the ballistic pendulum. It comprises of a heavy block of wood of mass M suspended by two long chords. A bullet of mass m is fired into the block horizontally. The block, with the bullet embedded in it, swings upwards. The centre of mass of the combination rises through a vertical distance h before coming to rest momentarily. In a particular experiment, a bullet of mass 40 gm is fired into a wooden block of mass 10 kg. The block is observed to rise by a height of 20.0 cm.

Initial speed of the bullet is

A

549 m/s

B

502 m/s

C

475 m/s

D

625 m/s

Text Solution

Verified by Experts

The correct Answer is:
B
`m u=(M+m)v=(M+m)sqrt(2gh)`
`rArr u=(M+m)/(m)sqrt(2gh)=(10+(40)/(1000))/((40)/(1000))xx sqrt(2xx10xx(20)/(100))=502 m//s`
`therefore` (B)
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Knowledge Check

  • A frequently used device to measure the speed of bullets is the ballistic pendulum. It comprises of a heavy block of wood of mass M suspended by two long chords. A bullet of mass m is fired into the block horizontally. The block, with the bullet embedded in it, swings upwards. The centre of mass of the combination rises through a vertical distance h before coming to rest momentarily. In a particular experiment, a bullet of mass 40 gm is fired into a wooden block of mass 10 kg. The block is observed to rise by a height of 20.0 cm. Fraction of initial energy lost in the collision

    A
    `0.9880`
    B
    `0.9960`
    C
    `0.9040`
    D
    `0.9755`

  • A frequently used device to measure the speed of bullets is the ballistic pendulum. It comprises of a heavy block of wood of mass M suspended by two long chords. A bullet of mass m is fired into the block horizontally. The block, with the bullet embedded in it, swings upwards. The centre of mass of the combination rises through a vertical distance h before coming to rest momentarily. In a particular experiment, a bullet of mass 40 gm is fired into a wooden block of mass 10 kg. The block is observed to rise by a height of 20.0 cm. If the bullet penetrates the block to a depth of 3.0 cm, the approximate average force of resistance by the block of wood is

    A
    `8.2xx10^(4)N`
    B
    `32.4xx10^(4)N`
    C
    `64.8xx10^(4)N`
    D
    `16.8xx10^(4)N`

  • A bullet of mass m moving with velocity v strikes a suspended wooden block of mass M. If the block rises to a height h, the initial velocity of the block will be

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    ` sqrt( 2gh ) `
    B
    ` (M+m)/( m) sqrt( gh ) `
    C
    ` ( m )/( M+m) 2gh `
    D
    ` (M+m)/( M) sqrt( 2gh) `

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