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 2.6 revolutions
in the first second after the stop function is
activated?

Answer 1

Hi! Out of curiosity, what subject is this, @michelle.k ?

Answer 2

algebra 2

Answer 3

Okay, thanks!

Have you tried to start this problem yet?

Answer 4

no. I don't really understand it to be honest

Answer 5

I'm working on it :)

The first step is to understand the situation.

The second step is to catch it in math.

Answer 6

OKAY

Answer 7

I don't think my brain is functioning well enough for this problem! Keep bumping it!

Answer 8

Have you done logarithms, yet?

Answer 9

Seems to me this would run out as follows...2.6 in the first second, then 1.3 in the next second, then .65 in the next second and so on as it would decrease by 1/2 from the previous second. Theoretically it would never stop. Have to work on the formula for this.

Answer 10

it is a geometric series.

Answer 11

Since we know \[
a_{n+1}=\frac 12a_{n}
\]

Answer 12

We also know that \(a_1=2.6\).

Answer 13

Even though technically the CD never comes to a stop, there are a certain number of revolutions it can make even given an infinite amount of time.

You need to remember the formula for infinite sums of geometric series.

Answer 14

Geometric series come in the form \[
a_n = a_1r^{n-1}
\]And we know \(a_1=2.6\) and \(r=1/2\).

Answer 15

OK SO THE ANSWER WOULD BE?

Answer 16

Are you kidding me?

Everyone on this here has become a little more stupid, because you asked for a straight answer after being given an explanation.

Answer 17

Try asking another question... such as whatever is stopping you from getting the answer yourself.

Answer 18

IM SO SORRY... I HAD TO USE THE RESTROOM AND WHEN I CAME BACK I HAD ALL THESE EXPLANTATIONS I DIDNT KNOW. I APOLOGIZE

Answer 19

DO YOU MIND BREAKING IT DOWN FOR ME AGAIN ? I WASNT AT THE COMPUTER SCREEN. my stomach was irritating me so I had to use the bathroom

Answer 20

Reread what I said. It is still there.

Answer 21

wouldnt r be 1/2?

Answer 22

I said that.

Answer 23

Do you know the equation then for infinite geometric sequence?

Answer 24

yes
s= a/1-r