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Homework Help: Rubber stopper hanging from the view view mirror of a car

  1. Jul 13, 2010 #1
    1. The problem statement, all variables and given/known data

    A 18g rubber stopper is suspended by a 45-cm string from the rear view mirror of a car. As the car accelerates eastward, the string makes an angle of 5.1 degrees with the vertical. Determine the acceleration of the car.


    2. Relevant equations



    3. The attempt at a solution

    I'm totally stumped. There are no forces or anything given, not even sure what the diagram should look like : |. Help !
     
  2. jcsd
  3. Jul 13, 2010 #2

    Doc Al

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    What forces act on the stopper?
     
  4. Jul 13, 2010 #3
    Gravity?
    And it's positioned at an angle because of inertia ? I don't think that can be drawn out as a force though.
     
  5. Jul 13, 2010 #4

    Doc Al

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    Yes, gravity is one of the two forces acting on the stopper. What's the other? (What's attached to the stopper?)
     
  6. Jul 13, 2010 #5
    Oh right, tension !

    So, from the rubber stopper, a force point outward diagonally (along the string) is the force of tension.
    And a force pointing directly downwards is gravity?
     
  7. Jul 13, 2010 #6

    Doc Al

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    Exactly!
     
  8. Jul 13, 2010 #7
    Oh okay! One more thing --the length of the string is given. I get confused when questions about the magnitude of forces give me the length or distance of something. I'm not sure what I can do with that?
     
  9. Jul 13, 2010 #8

    Doc Al

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    Just analyze the forces as you normally would. Ignore any extraneous information given.
     
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