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Conservation of Energy

  1. Mar 13, 2007 #1
    A block, mass 0.75 kg, is "shot" from a spring gun from a table. The table has a height 1.04 m and is frictionless. If the spring has k=28 N/m and is originally compressed 0.23 m, how fast will the block be goign when it hits the ground?

    (1/2)*kx^2 = (1/2)mv^2 ?????????????

    I got 4.3 m/s but the answer is 4.73 m/s
  2. jcsd
  3. Mar 13, 2007 #2
    If you show us your work, we can say where you've gone wrong.
  4. Mar 13, 2007 #3
    (23*0.23^2)/2= (0.75*9.8*1.04)+(0.7*v^2)/2
  5. Mar 13, 2007 #4


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    Hint: you have to "count in" the height of the table somehow in your calculation.
  6. Mar 13, 2007 #5
    Are you sure?? You need to find the velocity at the bottom and not at 1.04m. Also, k = 28N/m, not 23.
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