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Why does a heavier sphere fall faster in a liquid ?

  1. Dec 14, 2014 #1
    why do heavier balls fall faster in liquids ?, if F=mg-drag, a heavier ball would have greater mg, but the acceleration is given by F=ma, therefore mg-drag = ma, a = (mg-drag)/m.
    I cant see how a heavier ball would fall faster.
     
  2. jcsd
  3. Dec 14, 2014 #2

    Bandersnatch

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    You've got ##a=g-F_D/m##. (minus is up here) If you increase mass, g is reduced more or less?
     
  4. Dec 14, 2014 #3
    [itex] F=ma=mg-F_b-F_d [/itex] where [itex] F_b [/itex] is bouyant force and [itex] F_d [/itex] is drag.

    Then; [itex] a=g-F_b/m+F_d/m [/itex], so if you have two balls of same volume but different mass, the larger mass will have a higher acceleration.
     
  5. Dec 14, 2014 #4
    g is constant, but Fd/m is reduced, I see it now :D thanks.
     
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