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Homework Help: Tree cutting word problem

  1. Nov 16, 2011 #1
    1. The problem statement, all variables and given/known data

    a tall tree and a short tree of the same mass density and width are cut at the base at the same time. why does the small tree hit the ground first?

    2. Relevant equations

    none. its a word problem

    3. The attempt at a solution
    gravity id pushing in different ways?
     
  2. jcsd
  3. Nov 16, 2011 #2
    simple hint: How far does the top of the tree have to move for a small and for a large tree? could a tree that's twice as tall move twice as fast?

    harder: replace the tree with a pole with length l. suppose it's at an angle A from the vertical. Draw a free body diagram and find all the forces. You could also find the speed at angle A with conservation of energy. Solve the differential equation for the movement of the tree. (probably needs to be done numerically)
    A problem is what the initial angle, or the initial speed of the tree would be.
     
  4. Nov 16, 2011 #3

    phinds

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    saying that a word problem has no relevant equations is just silly. If there are no equations, then you are not going to get any answer.
     
  5. Nov 16, 2011 #4
    really? because the answer above you helped me and they didnt use any equations?
     
  6. Nov 16, 2011 #5

    phinds

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    Gold Member

    Yes, you're right, of course. I should have said, you won't get a quantitative answer. You'll notice that willem DID talk about equations. To really understand what's going on, you need the math.

    EDIT: And it IS silly to say that a word problem has no equations. If you don't understand that, you aren't going to get far in answering word problems.
     
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