Current Events > if I'm making a sine function and need to determine the period...

(+) Yeah! (+)

I calculated that my object goes 2.19 revolutions per second, but if I just do sin(2.19x) or sin((2pi/2.19)x), it doesn't look right - I am expecting it to complete two full cycles in one second.

if I do 1/4 of 2.19 then that looks right but I don't know if it is -_-

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Period is 1/frequency. 1 rev = 2 radians, so convert from rev/s to rad/s and you'll have your frequency

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Maybe I fudged my numbers up. ALSO... 2.19 was my sample duration, not the RPS.

I have 2.012 revolutions per second and then I calculated that that was 12.642 radians per second. (2.012 x 2pi).

But if I use 12.642...
Oh wait that actually looks right now wtf.

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Wether its a comma or a period its all fun right

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sabrestorm posted...

Wether its a comma or a period its all fun right

What are you talking about lmao

now I'm really doubting my numbers. I calculated that at 2.19 seconds it should have completed 4.4 revolutions, but on my graph it's coming up a little short...

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Hexenherz posted...

Maybe I fudged my numbers up. ALSO... 2.19 was my sample duration, not the RPS.

I have 2.012 revolutions per second and then I calculated that that was 12.642 radians per second. (2.012 x 2pi).

But if I use 12.642...
Oh wait that actually looks right now wtf.

At 12.642 rad/s you should have a period of 0.0709 seconds I believe

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I'm dumb and just read the discussion posts for the class and it looks like rad/s is the same as period.

But I'm also ... dumb and can't figure out the math on this shit, because the function I compiled does not align with the numbers I have somehow lmao.

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I've crunched my numbers a dozen times and it makes no sense why my graph should put the end of the second revolution just *before* the 1 second mark if it's supposed to be just *after* the 1 second mark.

Total distance traveled = 36 inches;
Diameter = 2.6 inches
Circumference = 8.168
Time = 2.19 seconds.

From this I concluded that the speed was 16.438 inches per second (36 inches / 2.19 seconds). From that, I concluded that the revolutions per second was 2.012 (16.438 inches per second / 8.168 inch circumference). Finally, took RPS and multiplied by 2pi for 12.64 radians per second.

So what I *expect* to see is a graph where it completes two cycles per 1 second, but it is completing two cycles in less than 1 second...

Granted, it's like 0.9942 seconds so I guess that's pretty damned close to 1 second but... still throwing my numbers off fam.

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Oh wait I'm fucking stupid, it's 2.whatever revolutions per second which means it *should* be less than 1 when I've had exactly 2 revolutions... I was looking at it the wrong way.

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