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Homework Help: Force / Work

  1. Mar 9, 2005 #1
    An arrow of mass 20 grams is shot horizontally into a bale of hay with a velocity of 60 m/s. It penetrates a debpt of 20 CM before stopping.

    What is the average stopping force acting on the arrow?

    I've been doing

    W = -F*D
    W = -(ma)*d

    I'm finding a by using a kinematic equation, v (final ) ^2 = v (initial ) ^ 2 + 2 a (delta) x.

    The answer I'm getting is 360 N, but that is not the correct answer. Any ideas?
    Last edited: Mar 9, 2005
  2. jcsd
  3. Mar 9, 2005 #2
    I'm an idiot. Never mind. I misread to work done by the stopping force. 180 is the right answer for those that care. There is no need for work at all, just a simple F = ma problem.
  4. Mar 9, 2005 #3
    If misreading the question makes one an idiot, i'm an idiot many times over for trasngressions as an undergrad :(
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