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Falling spade question

  1. Dec 11, 2011 #1
    "2 spades of the same type are dropped form the same height into the same patch of soil. why does the heavier spade have a lower acceleration in the soil than the lighter spade?"
     
  2. jcsd
  3. Dec 11, 2011 #2

    sophiecentaur

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    Hi and welcome.
    It might something to do with forces and masses. Think about Newton's laws of motion. Or you may like to consider Momentum. It depends upon your level of familiarity with Physics.
     
  4. Dec 11, 2011 #3
    What is the nature of the acceleration before the spade hits the ground? How about once the spade is in the soil?
     
  5. Dec 11, 2011 #4

    sophiecentaur

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    If we're not careful, the OP will just sit and watch as the full answer emerges so that he can just copy it down without thinking. We need to wait for a response now, I think.
     
  6. Dec 11, 2011 #5
    Well. Forces wise, there's the weight and soil resistance. Before hitting the soil, it's just weight. After hitting the soil, it's hindered by resistance?

    Ohh, Newton's Second Law of Motion?
     
  7. Dec 11, 2011 #6

    russ_watters

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    Look at the equation...
     
  8. Dec 11, 2011 #7

    sophiecentaur

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    Yews - Newton II: f=ma (rearrange it to get what you need)
    How will the forces on the spades differ and how will the masses differ? That should tell you whether there will be any difference in the acceleration (slowing down, that is).
     
  9. Dec 11, 2011 #8
    Ah I see it.
    mg-R = ma
    a = mg-R / m
    When m increases, a decreases.
    Which makes a more negative, bigger deceleration?

    Naww, I am not sure. Should it be R-mg then?
     
  10. Dec 11, 2011 #9

    sophiecentaur

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    It's mg-R, if you're considering 'down' as positive. This consistent if you were accelerating at mg.
    So you got it. Good.
     
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