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Simple harmonic motion and amplitude

  1. Apr 2, 2010 #1
    1. The problem statement, all variables and given/known data

    A 2.10-kg block is suspended from a spring with a spring constant of 280.0 N/m. A 0.070-kg bullet is fired into the block from directly below with a speed of 220.0 m/s and is embedded in the block. Find the amplitude of the subsequent motion.

    -What fraction of the original kinetic energy of the bullet appears as mechanical energy in the system of block-spring-bullet?

    2. Relevant equations

    we are learning about the oscillations and energy. For this question i'm thinking I would need to use E= Kinetic energy + potential energy.... (1/2)KA2=(1/2)mv2 + (1/2)Kx2
    but I don't know what to do to get started, I am soo lost!
    3. The attempt at a solution
     
  2. jcsd
  3. Apr 2, 2010 #2

    Doc Al

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    Staff: Mentor

    Start by finding the speed of the "bullet + block" immediately after the bullet embeds itself in the block. What's conserved during that 'collision'?
     
  4. Apr 2, 2010 #3
    I suggest using conservation of momentum on the collision between the bullet and block to find the initial velocity upwards of the block.
     
  5. Apr 7, 2010 #4
    thanks! but then how would I find part b? would I find the kinetic energy of the bullet and the mechanical energy of the system(in which I would plug back in my value for the amplitude?)
     
  6. Apr 8, 2010 #5

    Doc Al

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    Staff: Mentor

    Compare the KE before and after the collision.
     
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