Change in gravitional potential energy at an angle?

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

    A 0.23kg pendulum bob is attached to a string 1.2 long at an angle of 30 degrees. What is the change in the gravitational potential energy of the system as the bob swings from point A to point B
    U=
    2. Relevant equations

    .5 mv^2 = mgl
    U=E+K


    3. The attempt at a solution

    in the picture it looks like a string attached to a roof with the ball at rest touching the roof and swinging down to a position 35 degrees below im just not sure how you use the angle of 35 in the problem
     
  2. jcsd
  3. Hootenanny

    Hootenanny 9,681
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    Can you relate the change in angle to the change in height of the bob?
     
  4. the height isnt given its just the length of the string sorry.
     
  5. Hootenanny

    Hootenanny 9,681
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    I know it isn't given, what I was saying is can you work it out using the angle and the length of the string?
     
  6. would you do that my x sin theta ?

    im just really frustrated with this question
     
  7. Hootenanny

    Hootenanny 9,681
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    I'm not sure what my is meant to be, but yes you should use trigonometry.
     
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