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# A Simple Pendulum watch

1. Hi guys. I have a question that I'd like to ask you. I'm doing my coursework (GCSE) and I'm a bit stuck (quite literally) on the analysis section, where I have to explain what I have done etc. The aim of the experiment is to determine the value of acceleration due to gravity - that's the easy bit. I'm stuck on the section where I have to explain why the time period of the simple pendulum increases as the length increases. I have explained it using the T = 2π√l/g saying that g and 2π are constants and ∴ as l increases, so must the time period but my teacher says that I need to add more than this i.e. a fuller broader explanation as to why this is the case. I can't think of anything. I've been slogging for hours but its yielded no results. I've tried to see how the height and distance travelled by the pendulum varies as its length varies. I've tried to calculate the speed of the pendulum but I don't know how to go about this. If you have any suggestions, answers or tips, they would be very very much appreciated.
2. (Original post by senny99)
Hi guys. I have a question that I'd like to ask you. I'm doing my coursework (GCSE) and I'm a bit stuck (quite literally) on the analysis section, where I have to explain what I have done etc. The aim of the experiment is to determine the value of acceleration due to gravity - that's the easy bit. I'm stuck on the section where I have to explain why the time period of the simple pendulum increases as the length increases. I have explained it using the T = 2π√l/g saying that g and 2π are constants and ∴ as l increases, so must the time period but my teacher says that I need to add more than this i.e. a fuller broader explanation as to why this is the case. I can't think of anything. I've been slogging for hours but its yielded no results. I've tried to see how the height and distance travelled by the pendulum varies as its length varies. I've tried to calculate the speed of the pendulum but I don't know how to go about this. If you have any suggestions, answers or tips, they would be very very much appreciated.
Maybe your teacher is expecting you to derive the relation T=2(pi)root l/g?

I dont see that there is much else you can say. Clearly that formula only works for small angles and assuming no damping - so maybe you could mention that . Also if you plot a graph of T^2 against l it should be a straight line from the above equation - so you could try doing that. The gradient should be 4pi^2/g so you could then calculate an experimental value of g to see how accurate your results are. ie it should compare well to g=9.81
3. All the stuff that you have mentioned I have done in my coursework. Is there anything else you can think of?
4. (Original post by senny99)
All the stuff that you have mentioned I have done in my coursework. Is there anything else you can think of?
well you could start going on about A-level stuff. Ie the fact that the displacement with time is simple harmonic so that its acceleration is always towards the equilibrium position and is proportional to the distance from the equilibrium position.

Ie.

a= -(w^2)x where w is 1/T
If you solve that (which is above GCSE by quite a level) you get

x=Acostheta

where theta is the angle of displacement from the equilibrium. Its a cos and so it oscillates. You could find the speed in a similar way by just differentiating the above. But as I said that is at a much much higher level than would be expected of you.

Apart from that I cant really think of anything. Did your teacher not give any hints of what else you could add?
5. (which is above GCSE by quite a level)
Yeah. The maths is AS Further Maths!
6. (Original post by samd)
Yeah. The maths is AS Further Maths!
or just plain old A2 maths. You do it at the very beginning of Physics A2, well I did. I know its very advanced & Im not really saying it should go in. Its just to me the only thing you could expand upon - at GCSE I dont see anything you can add to what has already been said.

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Updated: November 18, 2005
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