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Homework Help: Bullet Hits Block Attached to Spring What am I doing wrong?

  1. Apr 24, 2012 #1
    A wooden block of mass M = 1.83 kg is rest on a frictionless, horizontal table attached to the end of an unstretched spring (k = 217 N/m). A bullet of mass m = 8.02 g is fired horizontally into the block at speed vo = 394 m/s. The bullet comes to rest inside the block, and causes the mass to oscillate on the spring. If there is no friction between the block and the table: find A, the amplitude of the resulting oscillation. You can assume the mass never hits the wall (to which the spring is attached.)

    Here is what I did, and I really don't see how this is wrong...

    By conservation of momentum --> m1v1 = (m1 + m2)v2
    (.0082)(394) = (1.83 + .0082)v2
    v2 = 1.75759m/s

    1/2mv^2 = 1/2kA^2

    (1/2)(1.83802)(1.75759)^2 = (1/2)(217)A^2

    A = .162m

    How is this wrong??
  2. jcsd
  3. Apr 24, 2012 #2


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    Staff: Mentor

    Check the mass value for the bullet that you used in the calculation of v2.
  4. Apr 24, 2012 #3


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    Homework Helper

    You dropped a zero from the mass of the bullet.

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