1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    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

    User Avatar

    Staff: Mentor

    Just analyze the forces as you normally would. Ignore any extraneous information given.
     
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook