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Air track - Inclined Plane experiment

  1. Nov 16, 2016 #1
    1. The problem statement, all variables and given/known data
    I am about to do an experiment where we masure the average speed of a cart released from the top of an inclined plane that has little friction (air track). The speed measurement is done by a photo gate. This is repeated a hundred times.

    2. Relevant equations

    I need to come up with a way to check how the air flow from the air track affects the movement of the cart. More accurately - I need to check how to air flow affects the random error of the speed measurements.


    3. The attempt at a solution

    I could calculate the difference between theory and experiment and find out how everything other than plane's friction and problems' parameters affect the movement. But I cannot isolate the air flow.
    Any ideas?
     
  2. jcsd
  3. Nov 16, 2016 #2

    Simon Bridge

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    Welcome to PF;
    Are you measuring the average speed for the trip down the inclined track or are you measuring the average speed through a photogate at the bottom of the track?

    Why do you need to isolate the air flow? What are you trying to isolate it from? What are the sources of error in this experiment?
     
  4. Nov 17, 2016 #3
    I'm measuring the average speed average speed through a photogate in a fixed point somewhere in the middle of the track.
    I was asked to make measurements that isolate the air flow. Other sources of error are: friction between the cart and the track, air friction, errors when measuring the incline of the track (accuracy of the ruler), enviornment causes such as table movement.
     
  5. Nov 17, 2016 #4

    Nidum

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    Please post a clear diagram or picture of your experimental set up .
     
  6. Nov 17, 2016 #5
    Untitled.png
     
  7. Nov 17, 2016 #6

    Nidum

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    But how does the air rail work ?
     
  8. Nov 17, 2016 #7

    Simon Bridge

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    I am confused you say you have friction from the air rail separate from the effect of the air.
    Does the cart touch the track?

    Anyway - yuor approach is first to understand how the air rail works - how might the air affect things?
    It is unclear from the question what is being asked of you.
    You have to isolate the effect of the air flow on what aspect of the motion?
    ie. do you need to isolate it's contribution to the uncertainty on speed measurements?
    Are you supposed to rework the experiment design to reveal how the passage through the photogate is affected by the airflow?
    What do they mean by "airflow"? Speed of the jets? Spacing of the jets? Volume of air per second through the machine?
     
  9. Nov 18, 2016 #8

    andrevdh

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    PhysicEng I think you have got it right, that is the influence of the airflow will show up in the randomness of the errors since any variation in the support of the cart by the airflow will change the recorder speed. It might also change if atmospheric conditions change - pressure, temperature, humidity....
     
  10. Nov 18, 2016 #9

    Nidum

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  11. Nov 18, 2016 #10

    Nidum

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    If this type of track is set up properly the drag on the cart is not going to be very much in most cases .

    Interesting though that there are jets of air at a regular pitch along the rail . As the cart arrives and departs from each jet position there could be a small amount of propulsion/retardation and a small amount of up/down motion . Probably too small to worry about in the proposed experiment but I think it would show up in a detailed motion analysis .

    It might be interesting to experiment with carts of same weight but different lengths .
     
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