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Mass and free fall question

  1. Feb 7, 2008 #1
    A ball of mass .5 kg is dropped from a height of 5 m. What is the greatest velocity it will have just before hitting the ground?

    vf squared = vi squared + 2ad

    vf squared = 0 squared + 2(9.8)(5)

    vf = 9.8 m/s

    So the greatest velocity is 9.8 m/s, right?

    I am still very confuzzled and I think this is the right answer because where did the mass go? Or it doesn't even matter? Can someone verify?

    Thanks!
     
  2. jcsd
  3. Feb 7, 2008 #2

    rl.bhat

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    Yes. Mass does not matter in the free fall under gravity. All the body get accelerated equally.
     
  4. Feb 7, 2008 #3

    Dick

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    Welcome to the forums! No, mass doesn't matter. The acceleration downwards is g, independent of mass, ask Galileo. It's a purely kinematical problem.
     
  5. Feb 7, 2008 #4
    Thanks! So is my answer correct?
     
  6. Feb 7, 2008 #5

    Dick

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    Approximately, yes. I would round the answer to 9.9m/sec. But that's a detail.
     
  7. Feb 7, 2008 #6
    Sweet! Thanks!
     
  8. Feb 7, 2008 #7
    I don't know why the question had mass in it. Trick question or something haha.
     
  9. Feb 7, 2008 #8

    Dick

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    In real world problems YOU have to figure out what's important and what isn't. It's just practice.
     
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