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What was Martha’s displacement before turning around?

  1. Aug 4, 2017 #1
    1. The problem statement, all variables and given/known data
    Use the following information to construct any necessary graphs to help you complete the next four questions.

    Martha leaves her house and drives with a constant velocity due east at 15 m/s for 85 seconds. She realizes she forgot something at home and stops the car in 6.5 seconds, makes a u-turn and then accelerates at 0.25 m/ss until she arrives back at home.

    What was Martha’s displacement before turning around?

    2. Relevant equations
    d= vt+1/2 at^2

    3. The attempt at a solution
    tried using the displacement equation initial velocity acceleration but didnt get it right
    Not sure what graph to use position vs time or what?

    (15 m/s)(91.5 s)+1/2(.1639 m/s^2)(8.37 s^2) =d
    2058.60589 =d
     
    Last edited: Aug 4, 2017
  2. jcsd
  3. Aug 4, 2017 #2

    TSny

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    Please list the "relevant equations" in section 2. Show your work in section 3 so that we can see where you are making a mistake.
     
  4. Aug 4, 2017 #3

    TSny

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    Can you elaborate on how you got the expression on the left? What does the first term represent? How did you get the values .1639 m/s2 and 8.37 s2 in the second term?
     
  5. Aug 10, 2017 #4
    used d=vt+1/2 at^2
     
  6. Aug 10, 2017 #5

    TSny

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    What is the value of the acceleration during the first 85 seconds of the trip? Please explain your answer.

    What is the value of the acceleration during the next 6.5 seconds of the trip? Please explain your answer.
     
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