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How high is the tree branch(conservation in energy/kinematics)

  1. May 31, 2012 #1
    1. The problem statement, all variables and given/known data
    45a)
    A watermelon with a mass of 2 kg falls out of a tree house that is 5.4 m above the ground. What is the speed of the watermelon just before it hits the ground.
    (this part i have solved)

    mass = 2kg
    Δd= 5.4m
    v=?

    v1^2 =v2^2+2gΔd

    v1^2=0+2gΔd

    =0+2(9.8)(5.4)

    v1^2=√105.84

    v1^2=10.28 m/s


    Now on to the part i didnt quite get.

    45b) A cantaloupe with a mass of 0.45kg falls out of the other side of the tree house. It hits a tree branch at a speed of 6.3 m/s. How high is the tree branch from the ground?


    2. Relevant equations

    v1^2 =v2^2+2gΔd


    v1^2-v2^2/2g=Δd


    3. The attempt at a solution



    45b)

    v1=0m/s

    v2=6.3m/s

    mass = 0.45 kg

    v1^2-v2^2/2g=Δd

    v1^2-v2^2/2g=Δd

    6.3^2-0/2g=Δd


    6.3^2/2(9.8)=Δd


    6.3^2/19.6=Δd


    39.69/19.6=Δd


    2.025m = Δd

    thats the height i got, if it is not correct, can someone show me how to get the right height? or better yet get the right height and i can analyze and figure out how you got the right height?
     
  2. jcsd
  3. May 31, 2012 #2
    Hi supernova1203. That would be the height from the branch to the treehouse, the question asks for the height of the branch from the ground.
     
  4. May 31, 2012 #3
    http://img15.imageshack.us/img15/5184/58649625.jpg [Broken]
    Just click icon above and you can creat beautiful equations
    Example
    v then click icon X2 above and filled the exponent intended, between SUB] and[/SUB. Here i put 2.
    v2
     
    Last edited by a moderator: May 6, 2017
  5. Jun 1, 2012 #4

    Tell me how did you come to that conclusion?

    ah....so in order to get the height from the branch to the ground, i would have to subtract the 2 heights...max height and the 2nd height i got for part B of the question?
     
  6. Jun 1, 2012 #5
    " A cantaloupe with a mass of 0.45kg falls out of the other side of the tree house. " The tree house is 5.4m above the ground from a), so I think by other side of the tree house just means it is dropped from the same height as in a). And yes that is the answer
     
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