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Propelling a Paramecium: 3 -- Calculations

Page history last edited by Joe Redish 12 years, 7 months ago

First complete:

 

  1. Download the Excel spreadsheet,Paramecium.xlsx.  Copy out the formulas in row 7 (cells A7 through E7) and explain what each formula does in terms of the stepping rule for Newton's second law.
  2. The values in the spreadsheet are arbitrary -- not related to the paramecium -- but never mind.  For now we will just explore how changing the parameters change the curves.  Notice that the velocity settles down to a constant and the net force and acceleration go to zero.  Explain why this happens.  (The velocity it settles down to is vT and it's called the terminal velocity.)
  3. Notice two things about the velocity plot:  what value it goes to (vT) and how fast it settles down.  By changing the values for m, R, β, and Fappin the spreadsheet,  describe how these two things change as a function of each of these variables and why you think it does that.
  4. Now try the numbers you generated for your paramecium in part 2 of the problem (including using a small fraction of the time scale you found as dt).  Find a value of Fapp that gives a reasonable motion that settles down to a constant velocity in the time shown on the graph.  What is the value of Fapp and dt that you found?  Print out and include your graphs for the paramecium.

 

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