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Finding force

  1. Sep 27, 2007 #1

    lim

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    1. The problem statement, all variables and given/known data

    A 21.7 g arrow is shot through a 9.6 cm apple. If the arrow enters the apple at 38.5 m/s and emerges witha speed of 31.2 m/s in the same direction, what is the magnitude of the force with which the apple has resisted the arrow?

    2. Relevant equations
    vf^2 = vi^2 +2adeltax
    f= ma

    3. The attempt at a solution

    31.2^2 = 38.5^2 +2(9.6)a
    973.44 = 1482.25 + 19.2a
    a = -26.5
    ma=|-575|
    f= 575 N
     
  2. jcsd
  3. Sep 27, 2007 #2
    Your method of calculation is correct. However, you need to watch out for the units. Convert them into proper units.
     
  4. Sep 27, 2007 #3

    lim

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    So mass should be in kg, so .0217(-26.5) = |-0.575| = 0.575 N, but it still said it was wrong. Am I forgetting something else?
     
  5. Sep 27, 2007 #4
    Yes. The size of the apple. Convert that into m.
     
  6. Sep 27, 2007 #5

    lim

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    Oh! 57.51 N. Thanks for your help l46kok.
     
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