The linear velocity is the tangential velocity, namely if the curved track were laid out onto a straight line.
The question is reduced to:
At a radius of 3.2 cm, or 0.032m, how many complete turns the laser head goes through in a minute.
Each complete turn, when straightened out has a length of 2πr cm.
The laser goes through a linear distance of 1.25 m/s or 1.25*60 m/minute=75 m/min.
The number of turns in a minute is therefore
RPM
=(75 m/min ) / (2π*0.032 m /revolution)
=? rpm
A CD has to rotate under the readout-laser with a constant linear velocity of 1.25 m/s. If the laser is at a position 3.2 cm from the center of the disk, what are the revolutions per minute (rpms) of the disk?
Can someone please help me solve this problem step by step. The answer i got was 9.5 and it was incorrect.
9 answers
I got 3.7699rpm is that correct and if so do i round to two sig. figs
How did you get 3.7699?
75*2*pie*0.032 is that wrong?
correction: 75/2*pie*0.032
So what do you get for the answer?
3.769
I got the correct answer it was 376.9. Thanks for the help.
Hint:
(75 m/min ) / (2π*0.032 m /revolution)
means that
2π*0.032
are all in the denominator.
You have probably multiplied by 0.032 instead of dividing by it.
3.7 rpm is quite slow, almost 10 times slower than your grandmother's 33 1/3 gramophone record.
(75 m/min ) / (2π*0.032 m /revolution)
means that
2π*0.032
are all in the denominator.
You have probably multiplied by 0.032 instead of dividing by it.
3.7 rpm is quite slow, almost 10 times slower than your grandmother's 33 1/3 gramophone record.