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Jasminebunnies

  • 3 years ago

Conservation of Mechanical Energy: A pendulum bob is released from some initial height such that the speed of the bob at the bottom of the swing is 1.9m/s. What is the initial height of the bob?

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  1. imron07
    • 3 years ago
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    |dw:1349481173829:dw|

  2. Jasminebunnies
    • 3 years ago
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    Why would K(A) be 0?

  3. imron07
    • 3 years ago
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    Yes, it 'released' without initial speed right?

  4. Jasminebunnies
    • 3 years ago
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    isnt the initial speed 1.9 m/s?

  5. imron07
    • 3 years ago
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    No, that's the speed at B.

  6. Jasminebunnies
    • 3 years ago
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    oh ok so you got the zero from A?

  7. imron07
    • 3 years ago
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    Yup :)

  8. Jasminebunnies
    • 3 years ago
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    but the book says tha answer is 0.18m but how would you get that answer?

  9. Jasminebunnies
    • 3 years ago
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    *the

  10. imron07
    • 3 years ago
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    I got the same answer. I wrote the formula at the picture:\[h=\frac{v^2}{2g}\]

  11. Decart
    • 3 years ago
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    when it comes to a pendulum does it not depend on the lenght of the string?

  12. Decart
    • 3 years ago
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    U=mgl

  13. Jasminebunnies
    • 3 years ago
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    ok, so you would use that formula, h=v^2/2g to get 0.18m?

  14. imron07
    • 3 years ago
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    @Jasminebunnies : Yes

  15. Jasminebunnies
    • 3 years ago
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    ohhh ok and the zero is put there because there is no mass?

  16. imron07
    • 3 years ago
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    Omg! (^ ^!) Which zero?

  17. Jasminebunnies
    • 3 years ago
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    lol! the zero in your original equation that you said came from A, in front of mgh

  18. imron07
    • 3 years ago
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    That's because v=0 at highest point.

  19. Jasminebunnies
    • 3 years ago
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    ohhh ok, is that because it has not been released at that point?

  20. Jasminebunnies
    • 3 years ago
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    @imron07

  21. imron07
    • 3 years ago
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    Because by the time the pendulum is released, the velocity is zero. It start from rest.

  22. Jasminebunnies
    • 3 years ago
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    yes, ok! thank you! I understand now :)

  23. imron07
    • 3 years ago
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    ok ;)

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