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Homework Help: Ridiculously simple acceleration and velocity vectors, but I can't get them

  1. Sep 28, 2008 #1
    Ridiculously simple acceleration and velocity vectors, but I can't get them....

    We're supposed to answer a series of questions based on this diagram, but I am so confused by the answers.

    1. The problem statement, all variables and given/known data

    A car travels at constant speed along the curved path shown in the figure below. Five possible vectors are also shown in the figure; the letter E represents the zero vector.

    jfk.Figure.03.U31EOC.jpg

    These are the 3 questions (along with the correct answers from the key):

    1. Which vector best represents the car's acceleration at point 1?
    answer: E

    2. Which vector best represents the car's acceleration at point 2?
    answer: D

    3. Which vector best represents the car's acceleration at point 3?
    answer: A

    I don't get these answers at all, first the question tells me the car is traveling at a constant speed, (which I answered in question 1, E) Then it says it's D for question 2, then it's A for question 3? I don't get how these vectors connect together at all, and it's completely stumped me.

    Thanks.
     
  2. jcsd
  3. Sep 28, 2008 #2
    Re: Ridiculously simple acceleration and velocity vectors, but I can't get them....

    Remember, velocity is a vector quantity. It has magnitude and direction. If direction is changing, then the velocity is changing. If the velocity is changing, then there must be non-zero acceleration.

    The car is experiencing centripetal acceleration at 2 and 3. Centripetal acceleration is always directed toward the center of the turn, at a right angle to the direction of motion.
     
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