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Consider two cars one a chevy, one a Ford. The Chevy is speeding along

  1. Sep 13, 2011 #1
    Consider two cars one a chevy, one a Ford. The Chevy is speeding along at 50m/s (mph) and the Ford is going half the speed at 30m/s. If the two cars brake to a stop with the same constant acceleration, are either the amount of time required to come to a stop, or the distance traveled prior to stopping influenced by their initial velocity.

    I don't really understand the concept of what the question is asking. And no this is not a Homework question.
     
  2. jcsd
  3. Sep 13, 2011 #2

    DaveC426913

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    Re: Velocity

    Is it simply trying to parse the poorly worded paragraph? Here it is broken apart.


    Consider two cars one a chevy, one a Ford. The Chevy is speeding along at 50m/s (mph) and the Ford is going half the speed at 30m/s. The two cars brake to a stop with the same constant acceleration.

    Is the amount of time required for each vehicle to come to a stop influenced by its initial velocity? Y/N

    Prior to each vehicle stopping is the distance it traveled influenced by its initial velocity? Y/N
     
  4. Sep 14, 2011 #3

    rcgldr

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    Homework Helper

    Re: Velocity

    Not that important, but 30 is not half of 50.
     
  5. Sep 14, 2011 #4

    Ken G

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    Re: Velocity

    It sounds to me like the question is asking you, what things depend on your speed when you undergo constant deceleration? Constant acceleration allows us to use a collection of well-worn kinematical laws, and here are two:
    the change in v2 = 2 a s, where s is the distance traveled.
    the change in v = a t, where t is the time.
    In both cases, if you are interested in stopping, then v is just the initial velocity, and you get
    s = v2/2a
    t = v/a
    and you clearly see that both the stopping distance, and the stopping time, depend on initial velocity v. You can also see the point commonly stressed in driver's education-- the stopping distance is especially sensitive to initial v, so if you speed, you will have a hard time stopping before you hit an object a fixed distance in front of you.
     
  6. Sep 14, 2011 #5
    Re: Velocity

    Are the stopping distance and/or stopping time affected by a car's initial velocity?

    Kind of a long, confusing, mathematically unnecessary and inaccurate way of saying the above.
     
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