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1. Please can you help me on Question 3 on this jan 2009 paper.... i cant seem to get the right frequency! Jan 09 PA.pdf

THANKS!
2. Okay so on the trace in the paper you can see that there are 3 peaks telling you that in 10ms (that is 1x10^-2 s) there are 3 wavelengths past a set point.

Frequency is wavelengths past a set point per second, and you know that 10ms goes into 1s 100 times. Therefore you know the approx frequency to be 3 (in 0.01s) x 100 (to get to 1s) giving you a frequency of 300Hz.

Hope that helps.
3. Oh unless it means all the tiny wavelengths in which case it would be more like 1000Hz which seems more plausible

EDIT: ok just seen the mark scheme and seems I was way off, sorry I couldn't be helpful!
4. (Original post by Salmonidae)
Oh unless it means all the tiny wavelengths in which case it would be more like 10000Hz which seems more plausible

EDIT: ok just seen the mark scheme and seems I was way off, sorry I couldn't be helpful!
hmmm yes i did what you did at first, and now looking at the mark scheme, i think you have to count the tiny peaks... but still... i would not have worked that out in the exam!!
5. Yeah tough question. Is a legacy paper though!!
6. There are 5 small waves for every large one so the frequency of the small waves is 5 times that of the large.
The large wave is 300Hz meaning the smaller is about 1500Hz
You can also count 15 small waves to 3 large ones to get the same answer.
7. (Original post by Stonebridge)
There are 5 small waves for every large one so the frequency of the small waves is 5 times that of the large.
The large wave is 300Hz meaning the smaller is about 1500Hz
You can also count 15 small waves to 3 large ones to get the same answer.
Thanks! makes sense...
8. what people will do for pos reps.,
9. (Original post by Maphs)
what people will do for pos reps.,
well, i have to create interest.. or no-one will help me! Its a tough world... give some to get some.
10. really funny, i should use that technique some time, but what does that actually do to them if we give them a pos rating i dont see how that is beneficial to them??

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