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Homework Help: IB Physics Extended Essay - Terminal velocity experiment - ideas neede

  1. Aug 19, 2014 #1
    Hi. I decided a month or so ago, that I am going to do my physics extended essay on the topic of terminal velocity.

    However, at the moment I am not sure what experiment I can do. At the beginning I thought I would do an experiment where I would drop bodies made of cardboard with different surface area while keeping mass constant, and then different masses while keeping surface area constant, and then analyse their effect on terminal velocity. But now I am thinking that this is way too easy and simple for a Extended Essay, it is only sufficient for a normal class lab.

    Is there any way in which I can modify my experiment so it is better suited for extended essay. Perhaps making the theory a little bit more complex.

    Any ideas? I was thinking may be to make parachutes instead of dropping simple objects. I also thought of investigating terminal velocity in water (Stokes law)? Do you have any other ideas?

    Any ideas much appreciated.
  2. jcsd
  3. Aug 19, 2014 #2


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    You didn't mention the shapes of your cardboard objects. Varying that would open up a far greater study.
  4. Aug 20, 2014 #3
    Hi haruspex. Thanks for the suggestion. So when I change the shape, I change the drag coefficient which in turn influences the terminal velocity, right?
    This is definitely a good option. Any other ideas people? If not, then I can always try to do this option.
  5. Aug 20, 2014 #4


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    A classic experiment in physics is to determine the viscosity of oil/some liquid by dropping a ball bearing into it. The other experiment I know of is to drop filters and measure their speed with a motion sensor.
  6. Aug 20, 2014 #5


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    Just to say that I would definitely try to go for doing experiments in water and other liquids (if nothing else because it lets you fool around a bit ... also, liquid honey is a nice viscous medium, yum! :wink: ... some vegetable oil might be of interest too). This will allow you to study also how the drag coefficient varies with the medium and not only the shapes. Note that buoyancy will also depend on the liquid though so you would have to account for that too and you might have to restrict yourself to transparent liquids to have a reasonable experimental setup.
  7. Aug 30, 2014 #6
    I have decided that I will perform experiments changing shape. And that the medium I will use will be water, not air.

    But I am stuck how I am going to be able to make these objects. Clearly cardboard won't work because it does not sink and it is difficult to change its shape. I was thinking Plasticine clay or something like that? Any other ideas?

    Also I was wondering how I will be able to change the shape without changing the surface area. Wouldn't making the body more curvy also change its surface area?

    Thanks for help
  8. Sep 1, 2014 #7


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    Maybe you could use the same object (plastic/glass bottle, hollow egg shell) and load it with varying amounts of lead pellets to alter the weight and see how that influences the terminal velocity? Are you going to drop it into the water or vary the flow past the fixed stationary object?
  9. Sep 1, 2014 #8


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    My suggestions for your IB essay are as follows.
    Terminal velocity experiments in fluid and gases can be performed under 3 conditions:
    1. Objects reach terminal velocity with f=-bv. You can design experiment to demonstrate this.
    2. Onjects reach terminal velocity with f=-bv^2. You can design experiment to demonstrate this.
    3. Objects reach terminal velocity and go back up along their path of falling. You can design experiment to demonstrate this.
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