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Momentum problem

  1. Dec 8, 2003 #1
    A 6.56g bullet is fired horizontally into a 94.2 g wooden block that is initially at rest on a rough horizontal surface and connected to a massless spring of constant 70.4 N/m. If the bullet-block system compresses the spring by 1.16 m, what was the speed of the bullet just as it enters the block? Assume the coefficient of kinetic friction between the block surface is .485. Answer in units of m/s.

    how would you solve this with friction?

    is it still m1v1 = (m1+m2)v2? but im not sure how to incorporate the friction
  2. jcsd
  3. Dec 8, 2003 #2

    Doc Al

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    Staff: Mentor

    Yes, momentum is conserved during the collision.

    After the collision, consider what happens to the mechanical energy. The bullet+block starts off with purely KE. The friction force does work against the block, dissipating some energy. Whatever's left transforms into PE as the spring is compressed.
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