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Homework Help: Finding the Velocty of A swinging Object

  1. Mar 10, 2009 #1
    1. The problem statement, all variables and given/known data
    An object is attached to a string L long and starting perpendicular to the ground, was moved back 60 degrees to the left. What is maximum velocity of the object achieved?

    I used Potential Energy = Kinetic Energy from the top to the bottom since it starts with having potential energy from the beginning and converts it all to kinetic at the bottom so:

    So i tried Mass(Gravity)Height = 1/2Mass(Velocity^2)

    Solved for Velocity which equals

    Square root of plus or minus 2gh

    I'm stuck on finding H.

    Does everything look aright?
  2. jcsd
  3. Mar 10, 2009 #2


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    Homework Helper

    Make a drawing. Put in your string at an angle.

    What is the length projected along where the string hangs vertically?

    Isn't your height then L minus that projected length that you can get by a trig function of the angle?
  4. Mar 10, 2009 #3
    To find the height, use the triangle created when it is pulled back 60 degree. Measure the vertical height from the object to ceiling(or whatever the top is) and then just use some basic trig or the Pythagorean theorem.
  5. Mar 10, 2009 #4
    i see, clever. Thanks
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