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byerskm2

  • 2 years ago

An object is dropped from a tower of height 224 feet, subject to only the constant acceleration of −32 ft/sec2 due to gravity. (d) What should its initial velocity be in order to strike the ground after 1 second?

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  1. satellite73
    • 2 years ago
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    clearly the word "dropped" here is inappropriate, since they are asking what hthe initial velocity should be if it is dropped, the initial velocity is 0!!

  2. byerskm2
    • 2 years ago
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    http://i50.tinypic.com/34ip8a8.png

  3. byerskm2
    • 2 years ago
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    In order to reach the ground in 1 second the Vi would have to have a negative velocity of some value otherwise it would not be fast enough

  4. satellite73
    • 2 years ago
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    oh you put in the word "dropped" tsk tsk

  5. byerskm2
    • 2 years ago
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    I just can't find the corriect value

  6. byerskm2
    • 2 years ago
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    sorry that's what the question said

  7. byerskm2
    • 2 years ago
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    :P

  8. satellite73
    • 2 years ago
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    lets try this \[a(t)=-32, v(t)=-32t^2+v_0, p(t)=-16t^2+v_0t+224\]

  9. byerskm2
    • 2 years ago
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    yes

  10. satellite73
    • 2 years ago
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    or more commonly written \[h(t)=-16t^2+v_0t+224\]

  11. satellite73
    • 2 years ago
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    set equal to zero, then put \(t=1\) to solve for \(v_0\)

  12. byerskm2
    • 2 years ago
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    208?

  13. satellite73
    • 2 years ago
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    \[t^2-\frac{v_0}{16}-14=0\]

  14. satellite73
    • 2 years ago
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    oh no your answer will have a \(v_0\) in it

  15. byerskm2
    • 2 years ago
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    I plugged in 1 for t and got the 208

  16. satellite73
    • 2 years ago
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    oh wait, you are right put \(t=1\) set equal to 0 solve for \(v_0\)

  17. satellite73
    • 2 years ago
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    \[0=-16+v_0+224\] \[v_0=-208\]

  18. satellite73
    • 2 years ago
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    i see the problem it is negative and you put 208 i bet

  19. byerskm2
    • 2 years ago
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    Oh! Darn. I even said it have to be negative in the beginning didn't I? X(

  20. satellite73
    • 2 years ago
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    yes you did

  21. byerskm2
    • 2 years ago
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    I plugged it in :) it's right :P thanks! I knew I had to be right but I'm always missing some stupid detail!

  22. satellite73
    • 2 years ago
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    yw always good to have another pair of eyes

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