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What is k for the bottom spring?

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  1. Nov 1, 2016 #1
    1. The problem statement, all variables and given/known data
    A 5.0-kg block suspended from a spring scale is slowly lowered onto a vertical spring.
    Part A: What does the scale read before the block touches the vertical spring?
    (answer =49.1N)
    Part B: If the scale reads 32 N when the bottom spring is compressed 30 mm, what is k for the bottom spring?

    2. Relevant equations
    F=kx

    3. The attempt at a solution
    K=32/0.03= 1066.7N/m
     
  2. jcsd
  3. Nov 1, 2016 #2

    BvU

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    So would 32 N be the force the block exerts on the bottom spring ?
     
  4. Nov 1, 2016 #3
    thats what i interpret from the question, is that not correct?
     
  5. Nov 1, 2016 #4

    BvU

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    If the scale reads 32 N, and ##g## times the mass is 49.1 N ...
    Draw a diagram of the forces on the block.
     
  6. Nov 1, 2016 #5
    Both forces are acting down so would it be (32+49.)1/0.03=2703
     
  7. Nov 1, 2016 #6

    BvU

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    The scale is pulling the block up
    The bottom spring is pushing the block up
    The earth is pulling the block down
    Fnet = ma and the block is not accelerating
     
  8. Nov 1, 2016 #7
    Would it still not be what I did earlier
     
  9. Nov 1, 2016 #8

    BvU

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    No.
     
  10. Nov 1, 2016 #9
    why? what is the mistake, should the forces be subtracted
     
  11. Nov 1, 2016 #10

    BvU

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    upload_2016-11-1_20-13-51.png Draw the forces the scale and the spring exert. Which way do they point ?
     
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