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Homework Help: Investigating terminal velocity

  1. Nov 26, 2015 #1


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    1. The problem statement, all variables and given/known data
    So, we were given these instructions to find the terminal velocity reached by an object falling through the air:
    Equipment: bun-case; access to balance; calipers; metre rule; stopwatch.


    1. Record the mass of the bun-case
    2. Measure with a recorded precision the dimensions of the bun-case and draw a scale diagram of it.
    3. Drop the bun case from approximately 1m above the ground and observe its fall.
    4. Plan a method to time the fall of the bun case as accurately as possible.
    5. Time the descent of the bun-case from 1m and then in increments up to a maximum of 2m to give sufficient data for analysis.
    6. Plot a graph of time against height of drop
    7. Plot a graph of average speed against height of drop

    8. Use these graphs to estimate the terminal velocity and give your reasoning.

    But how do we do that?

    2. Relevant equations
    3. The attempt at a solution
    So, if you find the average speed (height/time) for each height at which you dropped it, eventually the average speed will plateau on the graph, equalling the terminal velocity?

    Or is there a different reason? Thank you!
  2. jcsd
  3. Nov 26, 2015 #2


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    It probably won't reach that plateau in this test, but maybe you can estimate where the plateau would be. Not sure if it is intended here, but that could involve having a mathematical model for how the velocity varies during the descent (based on theory) and fitting it to the data.
    Another approach does not involve finding average velocities, so again may not be what is sought. When you drop it from 1.1m, the first 1m should be exactly like the descent from 1m. What does that suggest?
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