Physics question (elasticity)

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    Unregistered Leeman_s's Avatar
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    Physics question (elasticity)

    What is the elasticity of a ball which hits a wall at 10 m/s and rebounds off the wall at 8 m/s? (answer to 2 significant digits)

    That's an online question for school. All of us trying to do it can't get it. It should be 80% I think, but it's not. And it's not a multiple choice question.

    Anyone know how you would do that?

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    Mayor of Awesometown Govtcheez's Avatar
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    5.

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    Unregistered Leeman_s's Avatar
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    What....? 5 is the answer? Huh? I can't make sense out of that...and it should be a two digit number (yes I know how sig figs work but I know that what my teacher implies by that)

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    64%

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    C++ Developer XSquared's Avatar
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    8.0x10^-1
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

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    C++ Developer XSquared's Avatar
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    Originally posted by ZerOrDie
    64%
    How'd you get that?
    Naturally I didn't feel inspired enough to read all the links for you, since I already slaved away for long hours under a blistering sun pressing the search button after typing four whole words! - Quzah

    You. Fetch me my copy of the Wall Street Journal. You two, fight to the death - Stewie

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    & the hat of GPL slaying Thantos's Avatar
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    3X


















    Now just have to solve for X.

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    Xei
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    e = ( 1 - ((EKInitial - EKFinal) / EKInitial)) *100 = x%

    We will substitute any mass. Lets say 1kg.

    EK = (1/2)mv^2

    EKInitial = (1/2)(1)(10)^2 = 50J
    EKFinal = (1/2)(1)(8^2) = 32J

    ((50 - 32) / 50) * 100 = 36%

    1 - .36 = .64
    .64 * 100 = 64%

    The ball has an elasticity of 64% (as 36% of the Kinetic energy was lost). Just remember your conservation of energy.
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    looks like someone took the time to explain my answer lol

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    Xei
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    Originally posted by ZerOrDie
    looks like someone took the time to explain my answer lol
    Yes. I had to look back on some previous work because I realized that I actually forgot how to calculate the elasticity of an object - which frusterated me to no end.
    "What are you after - the vague post of the week award?" - Salem
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    Unregistered Leeman_s's Avatar
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    im so mad. I even tried that, but it said it was incorrect so I reverted to 80%! I think it has problems with how you enter the answer, like it'd make a difference if it was 64, 64%, or 64 %

    That threw me off then, indeed!

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    Xei
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    Try .64
    "What are you after - the vague post of the week award?" - Salem
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    I don't know about angels, but it is fear that gives men wings.
    The problem with wanting something is the fear of losing it, or never having it. The thought makes you weak.

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