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Homework Help: Can anyone help me out on the simple pendulum lab?

  1. Nov 23, 2009 #1
    For the simple pendulum lab, I have to find the percent difference between my theoretical and experimental velocity. I found out my theoretical velocity as I used the conservation of energy to generate an equation for v, but I'm having a hard time calculating my velocity from my experimental data! So what happened was that a bob was swung at different angles (10° to 60°) with the bob going through a photogate. The time recorded was the time the moment the bob entered through the photogate. Using this time and other data present (pendulum length, radius of bob...) I have to find velocity, BUT I have no clue how to do so. I tried to find my time by finding the arc length (the length of the path travelled by the bob) divided by my time, but my answers are so way off from my theoretical. I really don't know what to do and I'm so frustrated... I would really appreciate if anyone could help me out on this one! Thank you!
  2. jcsd
  3. Nov 23, 2009 #2


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    One time is not sufficient to to extract velocity information from experimental data. The first time a photogate beam is interrupted, a clock starts running (that's t = 0). You need a second time and a length to determine speed. Exactly what times did you record?
    Last edited: Nov 23, 2009
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