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Homework Help: A ball is dropped from the top of a building...

  1. Sep 16, 2018 at 12:11 PM #1
    1. The problem statement, all variables and given/known data
    A ball is dropped from the top of a building and falls vertically downwards. Air resistance can be neglected. After falling a distance d, the speed of the ball is v. Determine the speed of the ball (in terms of v) when it has fallen a distance of 2d.

    2. Relevant equations

    3. The attempt at a solution
    We tried to isolate for V2 and d and then substitute them into each other but that didn't work. Please help!
  2. jcsd
  3. Sep 16, 2018 at 12:14 PM #2


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    You should show the relevant equations and what you did with them in your work.
  4. Sep 16, 2018 at 12:34 PM #3
    I'm sorry but whats a relevant equation? a=9.8m/s2 and V1=0m/s and I'm not sure what to put for d and V2 which is what we are solving for. Not sure if that helps?
  5. Sep 16, 2018 at 12:54 PM #4


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    Can you identify what kind of problem this is, e.g., what concepts are relevant? What do you mean by "university acceleration" in the title? You're referring to ##d##, ##v_1##, and ##v_2##. The variable ##d## is defined in the problem statement, but we'd have to guess what you mean by ##v_1## and ##v_2##.
  6. Sep 16, 2018 at 1:03 PM #5
    Im sorry im in grade 12 doing a "University" question. I just wrote down what the question asked me. I have no clue what to do. Sorry
  7. Sep 16, 2018 at 2:02 PM #6


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    Hint: Distance is the area under a graph of speed against time.
  8. Sep 16, 2018 at 2:09 PM #7


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    We are given information on both the distance fallen and on the final velocity. From that information [and an assumption of constant acceleration] it is possible to write down an expression for the actual acceleration. That acceleration might not be 9.8 m/s2.

    What are some equations that you know for motion under constant acceleration? Or for work, momentum and kinetic energy?
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