Creating a falling ball map
Pyth, 19 bytes

VQ.&gt;+*\_25*d5O30*b4


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Explanation


VQ.>+*\_25*d5O30*b4  # Q = input

VQ                   # Repeat Q times
     *\_25           # 25 underscores
          *d5        # 5 spaces
    +                # concat the underscores and spaces
  .>         O25     # rotate this string 0-29 times
                *b4  # print the seperating newlines