googoo: what is the period of a record whos frequency is 45RPM
RPM stands for revolutions per minute.
Frequency (f) = cycles per time period (1 cycle/sec = 1 Hertz)
Period (T) = time per cycle
that is
f = 1/T or T=1/f
So if the frequency is 45 Revs/1minute
then
Period = 1min/45revs = 1/45 minutes (per revolution) = 1.33seconds (correct to 2 dec places)
It is really seconds per revolution but the 'per revolution' part is just understood, you don't include it.
You could take a look at this web page. There are question on the site (with pop up answers) so that you can check if you understand.
http://www.physicsclassroom.com/class/waves/u10l2b.cfm
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