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# Amplitude of a Pendulum Watch

1. When taking readings of the maximum amplitude of a Pendulum in SHM, how would i go about increasing accuracy and reducing error in my readings? Is there anything i should use rather than just observing the height?
2. You are making a mistake there. The amplitude of the pendulum is the distance from the middle (equilibrium). So why are you measuring height? Also you can't really do much other than keeping the length of the string large so that the arc at which the pendulum travels is rather straight. After all, you are measuring the distance with a ruler.
3. so would you measure the arc length? would that be the amplitude?
4. (Original post by Christd)
When taking readings of the maximum amplitude of a Pendulum in SHM, how would i go about increasing accuracy and reducing error in my readings? Is there anything i should use rather than just observing the height?
(Original post by thephysicsguy)
You are making a mistake there. The amplitude of the pendulum is the distance from the middle (equilibrium). So why are you measuring height? Also you can't really do much other than keeping the length of the string large so that the arc at which the pendulum travels is rather straight. After all, you are measuring the distance with a ruler.
I also measured the height at which the bob reaches as the amplitude... although this is correct & would give the same graph.

I don't think this is the 'expected way' of getting the results... because it was so damn difficult for me to measure with a ruler (vertically).

Do you guys think I will get penalized for this in an ISA ?

...even if I get the same graph - I am worried as they give different results but also measuring it vertically gives me much small results- meaning a greater increased in uncertainty/ error!

5. (Original post by posthumus)
I also measured the height at which the bob reaches as the amplitude... although this is correct & would give the same graph.

I don't think this is the 'expected way' of getting the results... because it was so damn difficult for me to measure with a ruler (vertically).

Do you guys think I will get penalized for this in an ISA ?

...even if I get the same graph - I am worried as they give different results but also measuring it vertically gives me much small results- meaning a greater increased in uncertainty/ error!

Hey, as long as you exactly followed the instructions on the sheet given to you, your table is labelled correct, graph is labelled correctly, line of best fit is in the right place, units are correct and significant figures are constant you should not lose any marks even if all your readings are not completely correct. The results of the experiment you've conducted don't really matter that much. Once my graph came out as a curve and it was supposed to be a straight line so i just drew a line of best fit with equal amounts of points on each side and i got full marks. When measuring amplitude of a pendulum i think you're supposed to measure the height that the bob reaches after each oscillation. However, if you have the length of the string to the center of the bob (r) and the horizontal displacement (x) i think you can find the arc length using: r*sin^-1(x/r) however i don't think this is expected..
6. (Original post by Christd)
so would you measure the arc length? would that be the amplitude?
Not exactly, the amplitude is the displacement from equilibrium, so it is actually a perfect straight line from equilibrium to the bob.
7. (Original post by thephysicsguy)
Not exactly, the amplitude is the displacement from equilibrium, so it is actually a perfect straight line from equilibrium to the bob.
Ah thanks, that does make sense. If i were measuring the decay of amplitude against time, could not just take height as amplitude and measure the new height reached after each ocscillation..it would give a similar graph wouldn't it?

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Updated: April 18, 2013
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