frequency of a vibration

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Alex18

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I dont understand this. What frequency has the vibration 7*f in this picture? F=1/t but i cant use it for this.
 

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Perhaps you ought to pay attention in class, rather than getting other people to do your work for you!.
 
I dont ask for answers just for good advice on how to solve the task because I am stuck with what I have and i dont understand that. I have no class, i have holidays.
 
This is valid for any square wave. The frequency of the square wave is equal to 1 / period of the square wave.

Let's say the period is 0.01 seconds. The frequency is equal to 1/0.01 = 100 Hz. Hz = cycles/second.

If the amplitude of the square wave is 1 unit,
The sine waves comprising it are

100Hz at an amplitude of 1 +

300 Hz at an amplitude of 1/3 +

500 Hz at an amplitude of 1/5 +

700 Hz at an amplitude of 1/7 +

ad infinitum
 
The answer is right there in the attached picture. It is written in German. Time = 0,5ms in German but English = 0.5ms. .5ms is half of a full wave, do math to find full wave. 2x.5ms=1ms 7t is 7 times faster frequency.
 
Last edited:
I missed the time scale on the plot - sorry. It was 3:30 am when I posted that and I was looking at the plot through one blurry eye.

Gary is right. Half the period is 0.5mS, so the full period of the square wave is 1mS.

T = 1/f where

T = period in seconds

f = frequency in Hz (cycles/second)

Rearranging,

f = 1/T = 1/0.001 seconds = 1000 Hz.

1000 Hz is the fundamental frequency of the square wave. It can be broken down into sine waves of odd harmonics.
 
This plot shows an FFT - the frequency domain - of a square wave. Notice there's no energy at the e en harmonics of the fundamental frequency.
 
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