Recent content by jameslat

  1. J

    I Integrating FFT, python code

    Hi Mark, So the goal of this function is to accept the FFT of a discrete set of data points which represent an acceleration signal a(t) and find the position over time x(t). The input is fft(a(t))=a(w). I know that for ever harmonic in a(w), that the corresponding time domain signal is An(t) =...
  2. J

    I Integrating FFT, python code

    Hello, Thank you for taking time to read my post. I have a discrete set of data points that represent an acceleration signal. I want to take the integral of this set of points twice so as to get a function which represents the position over time. To accomplish this, I have taken the FFT of the...
  3. J

    I Extracting sinusoids from FFT

    will iFFT( FFT('O') * FFT(H) ), result in a backwards 9? I haven't ever find anything like that before. It seems interesting though.
  4. J

    I Extracting sinusoids from FFT

    Works perfectly! I can't believe that it was that straight forward. You have been very helpful. Here is my python code as a contribution to the community (this is obviously for a dummy signal): import numpy as n import matplotlib.pyplot as plt from scipy.fftpack import fft, ifft, fftfreq...
  5. J

    I Extracting sinusoids from FFT

    Hello, Thank you for taking time to read my post. Background: I have a accelerometer project that I am playing with that gives me the acceleration of the object. I can plot this data and it looks very nice. I want to integrate this to get the velocity and then integrate it again to get the...
  6. J

    Max force help

    Hello, I built a small potato cannon out of PVC pipe/steel. It's 15.5 cm long, and about 7.6 cm wide on the inside. It's made of 2 parts the barrel and combustion chamber (or as i refer to, "the death chamber"). the "death chamber" is cylinder about 7.6 cm long and 7.6 cm thick. and the...
  7. J

    Help with basic physics problem.

    MOST EXCELLENT! Thank you all so much for your time and patients:P
  8. J

    Help with basic physics problem.

    i thought i had to convert it to N/m much like you have to convert 57g to .057kg right?
  9. J

    Help with basic physics problem.

    ok so tell me if i do this right if i have a spring that has 1 lbs/in which equals 175.12 N/m and if I put that into this equation. (1/2)mv2 = (1/2)kx2 .5(.057)9.9^2=.5(175.12)x^2 then that x=.1786 which is roughly 7.03 inches. Is this all correct?
  10. J

    Help with basic physics problem.

    so if i have a 20 lbs/in spring that is one foot long i need to push it 1 foot back to get my 20 pounds of force?
  11. J

    Help with basic physics problem.

    what if i shaved my tennis balls (don't laugh) and lubed the pipe with a silicon based oil? (like they use for cleaning gun barrels, like waxing it) that would minimize friction wouldn't it? and yes it is getting just a bit. so pulling it back 12 inches gives a .285 lbs. So if a spring says...
  12. J

    Help with basic physics problem.

    http://www.boltscience.com/pages/convert.htm why is it when I try and input my work with this calculator (above) I get a huge error (like 300 lbs/in)? also would this be right then? (1/2)mv2 = (1/2)kx2 .5(.057)9.9^2 = 25x^2 x=.3342 so I would only need to pull it back .334 of a meter with a...
  13. J

    Help with basic physics problem.

    ok 50 N/m = 442.53 lbs/in (and vice versa) @cupid.callin so with (1/2)mv2 = (1/2)kx2 and mass=.057kg V=9.9 m/s k=50 I'd be write to do the equation and get (1/2).057*9.9^2 = (1/2)50x^2 x=.334 Would this be accurate? Thanks again (things are starting to get clearer)
  14. J

    Help with basic physics problem.

    ok the fact is I'm trying to build one of these at home and I want to find out what type of spring to buy. and my math didn't make any sense when it said 247 pound/in spring so i was hoping to find the right answer with you guys. But i guess to my dilemma no one can help me unless if I have...
  15. J

    Help with basic physics problem.

    So your saying 9.9 m/sec is wrong to begin with? Just a reminder I'm a HS student and my teacher just got done teaching us basic 2-d kinematics and now is moving into springs and forces and half the equations that r being presented to me I never even seen before in my life. "Physicists seldom...
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