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Moving Reference Frames: One Car Passing Another

  1. Sep 28, 2012 #1
    1. The problem statement, all variables and given/known data
    You are traveling in a car going at a constant speed of 100 km/hr down a long, straight highway. You pass another car going in the same direction which is traveling at a constant speed of 80 km/hr. As measured from your car’s reference frame this other car is traveling at -20 km/hr. What is the acceleration of your car as measured from the other car’s reference frame? What is the acceleration of the other car as measured from your car’s reference frame? Give an explanation to your answers.


    2. Relevant equations
    The only equation I personally have in my notes is at=aw or wt=wwt+ww. Note that I have no idea what these equations mean, I just scribbled them down as my professor flicked through the slides.


    3. The attempt at a solution
    I figured that my vehicle would be accelerating at 20 km/hr2, and the other car would be accelerating at -20 km/hr2. Is this correct? I am not sure if I am doing anything right.
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 28, 2012 #2

    HallsofIvy

    User Avatar
    Staff Emeritus
    Science Advisor

    Is that really the question? You are told that both cars are moving constant speed. While speed is "relative", acceleration is not! The acceleration of both cars is 0 in any reference frame.
     
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