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Speed of Objects

  1. Sep 6, 2013 #1
    As a stationary object, is it possible to determine the speed of an object as it approaches you? If so, how? ...and with accuracy?

    For instance, if I'm standing on the sidewalk, can I determine the speed of a car on the road as it approaches me?
  2. jcsd
  3. Sep 6, 2013 #2


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    Sure. Around here the traffic police use hand-held radar guns to catch speeders.
  4. Sep 6, 2013 #3


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    Time how long it takes the car to cover the distance between two objects (eg two lamp posts). Later measure the distance between the two lamp posts. Calculate the speed. The accuracy will be limited to how accurately you can measure the time. If the car casts a shadow on the lamp posts as it passes I'd suggest you can get quite an accurate measurement.
  5. Sep 6, 2013 #4


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    Some pictures and info to go along with Nugatory's reply: Doppler effect, Police RADAR.
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