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Homework Help: The hot-air ballon intersection question.

  1. Sep 4, 2010 #1
    I am close to positive I am going at this problem the correct way, but there seems to be some error somewhere. This problem is from online homework.

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

    A hot-air balloon has just lifted off and is rising at the constant rate of 2.2 m/s. Suddenly one of the passengers realizes she has left her camera on the ground. A friend picks it up and tosses it straight upward with an initial speed of 12 m/s.

    If the passenger is 2.5 m above her friend when the camera is tossed, how high is she when the camera reaches her?
    Express your answer using two significant figures.

    2. Relevant equations


    3. The attempt at a solution

    So I know I need to set the two equations equal and solve for time.


    Solving for t (using quad. equation) gives solutions as t=.3 , t= 1.7

    Now I plug the time into the first equation and solve for x for the hot-air balloon at .3 seconds.

    2.5+2.2(.3) = 3.16 m

    As should be the case, I get the same answer when figuring x for the camera:

    12(.3)-(.5)(9.81)(.3)^2= 3.158 m

    When I plug this answer into the online homework it says, "Not quite. Check through your calculations; you may have made a rounding error or used the wrong number of significant figures."

    I have tried the following answers, none of which work: 3.1, 3.15, 3.2


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

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. Sep 5, 2010 #2
    Your equation is correct. Since the online homework website is saying that you're having some kind of rounding error, I went on checking the values. It appears that the actual value should be approximately 3.16045. Try to input 3.16 as an answer there.
  4. Sep 5, 2010 #3
    I would have already tried that answer but the question asks for the answer to be in only two significant figures. "3.16" is three figures is it not (this significant figure thing is a bit confusing)?
  5. Sep 5, 2010 #4
    In case of 'two significant figures', the answer should definitely be 3.2
  6. Sep 5, 2010 #5
    Yeah Iv'e tried it....says incorrect.
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