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The mass of the pendulum bob was determined on an electronic scale and

  1. Jul 27, 2012 #1
    The mass of the pendulum bob was determined on an electronic scale and its diamter was measured using calipers. The initial height was measured with a meter stick. At the lowest point of its swing, the pendulum bob broke a photogate light beam. The time interval that the light was interrupted was recorded on an electronic timer attached to the photogate.
    Use the following data to complete a report.
    MAss of pendulum bob = 240.3 g
    Diameter of pendulum bob = 3.50 cm
    Initial height of pendulum bob = 48.0 cm
    Length of pendulum string = 2.14 m
    Time interval of photogate light interruption = 11.8 ms

    Your report should include the following:
    (a) conclusion as to whether or not the pendulum demonstrated the law of conservation of energy
    (b) calculations of the efficiency of the pendulum as a mechanical machine
    (c) any statements of sources of error
    (d) your suggestions for improving the design of the investigation.
    Relevant equations[/b]



    3. The attempt at a solution

    Am I supposed to perform this experiement myself, becuase they are giving me all the measurments (therefore am I just doing an analysis) I am not quite sure how to go a outs this since they give me everything

    To see if it obeys law of conservation Of energy I was going to see if the initial height matches the final hiring using 9.8m/s and my v ... Is that correct and how do I find efficnecy
     
  2. jcsd
  3. Jul 27, 2012 #2
    Re: Pendlulum

    Oh and I converted grams to kg and cm to m
     
  4. Jul 27, 2012 #3
    Re: Pendlulum

    the experiment has been carried out for you (imagine that you watched it happening). You are then going to process the results.

    I don't know what you mean by "final hiring using 9.8m/s"

    What "v" are you referring to? You have yet to give a calculation for v, or to say what v is.
     
  5. Jul 27, 2012 #4
    How do I calculate for v?
     
  6. Jul 27, 2012 #5
    Re: Pendlulum

    I know I use diameter and the 11.8 ms but I don't know the equation
     
  7. Jul 27, 2012 #6
    Re: Pendlulum

    err you introduced v. I don't know what you mean by v.

    By way of an extreme example I'm currently sitting still so my "v" I'd say was currently zero.
     
  8. Jul 27, 2012 #7


    So if I use this equation

    1/2mv^2+mgdeltah


    It look like this.

    0+0.3403 x 9.8m/s^2 x 0.48m?


    Which equals 1.6 j as its initial spot at a...
     
  9. Jul 27, 2012 #8
    Re: Pendlulum

    Then for final height I did

    0+ mgdeltah= 1.6J
    (0.3403)(9.8m/s^2)deltah=1.6J

    So delta h = 0.48 therefore it obeys the law?
     
  10. Jul 27, 2012 #9
    Re: Pendlulum

    I'm stuck here. I don't know what you mean. I can't help with equations or verifying any answer until I know what steps you plan on using to answer the pendulum problem you have been set.
     
  11. Jul 27, 2012 #10
    Re: Pendlulum

    That's what I used above ?? I don't understand why they gave me so much info
     
  12. Jul 27, 2012 #11
    Re: Pendlulum

    I've covered that...

     
  13. Jul 27, 2012 #12

    And you are saying I need v.. So how to I get that? What equation do I use?
     
  14. Jul 27, 2012 #13
    Re: Pendlulum

    You said you will use v in your opening post. You did not say what this v that you need is.

    You need to say what v is before anyone can help you calculate it.
     
  15. Jul 27, 2012 #14
    Re: Pendlulum

    So v is 0 for the first hieght. The starting hieght at 0.48m r 48cm .. Because it is not moving.


    I need to know what v is for the final so I can determine te hieght. So how do I find v when I have calculate the J for E mechancal. As posted above in previouse post
     
  16. Jul 27, 2012 #15
    Re: Pendlulum

    You still are not saying what v is. For example every pendulum I've ever seen eventually stops so my final value is going to be zero. But that does not help you because I haven't said what I mean by v. On one pendulum clock I saw the escapement broke and the pendulum was thrown across the room. Numbers alone have no meaning.

    Describe what you mean by v in words. Make it very clear so there can be no misunderstanding.
     
  17. Jul 27, 2012 #16
    Re: Pendlulum

    Ok v is speed sorry
     
  18. Jul 27, 2012 #17
    Re: Pendlulum

    speed of what?
     
  19. Jul 27, 2012 #18
    Re: Pendlulum

    Of the pendulum when it hits its final hieght ...
     
  20. Jul 27, 2012 #19
    Re: Pendlulum

    How will knowing that value help you? [You need a plan for how you are going to answer the question in your opening post]
     
  21. Jul 27, 2012 #20
    Re: Pendlulum

    Yes so my initial speed v is 0m/s as when it starts at intial hieght at 0.48m it is not moving. I need to find out the speed when it moves to the other side and need that hieght I determine if it obeys the law or not.
     
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