Question

In coming to rest, suppose that a CD makes one half as many revolutions in a second.
How many revolutions does the CD make in coming to rest if it makes 3.3 revolutions in the first second after the stop function is activated?

Answer 1

It looks like you're looking at a "half life" type problem, which uses the exponential growth and decay formula. The formula for that is \[p=p_0*e^{rt}\], where p is the current amount of material/population, \[p_0\] is the initial population, r is the percentage, and t is time in whatever your half life is measured in. The only problem is, technically with half life you never hit 0, so I'm not sure how that problem would be worked.

You'd start by saying that for time=1, you have 1/2 the starting amount, so \[1/2p_0=p_0e^{r*1}\], and solve for r by dividing out \[p_0\] then taking the natural log of both sides, to get ln(1/2)=r. Then you'd plug that in for your equation, and solve for time when p=0...but again, the problem is, that'll never happen in finite time

What level class is this for?

Answer 2

beyond my level....

Answer 3

The material I posted is at a precalculus level, not sure what level the question was on though.

Answer 4

it's algebra 2

Answer 5

yeah I do that next semester

Answer 6

Farabor over did the equation because it's not precal

Answer 7

I have no idea how to approach that question at the level they have you doing it then....sorry, hopefully someone who's used to taking/teaching that level can help!

(The horrors of being a grad student, been a long time since I touched high school math)

Answer 8

yes the horror

Answer 9

i am in 6th grade. not joking.
i know alg 2 but sorry i dont know this

Answer 10

any other math problems?

Answer 11

to me, it's 3.3/2 1.65 revolution /sec