Question

A dvd drive has a maximum speed of 72000 revolutions per minute. if a dvd has a diamter of 12 what is the linear speed

Answer 1

The question isn't clear enough, I think it ask us to calculate the linear speed of a point at the edge of the DVD.
Now let's imagine we're a point at the edge of the DVD, we're undergoing a circular motion. Each minute we will complete a circular track 7200 times, now we need to know the distance we travel each turn. The perimeter of the DVD, a circular object is:

`P=2\pi.R`
Know recall that:

`v=(d)/(t)`
We now need to know how much distance is traveled during a minute or 60 seconds:

`D=7200* 2\pi* R`
Finally we divide this result with t=60 seconds:

`v=(7200*2\pi* R)/(60) \\ R=(12)/(2)=6`

`v\approx 4523.89 (units)/(second)`
Where the distance units were named units as the length unit is not specified in this exercise.