# Homework Help: Circumference of cirlce

1. Oct 16, 2007

### soharu

1. The problem statement, all variables and given/known data
i know Circumference is C = pi . d
if i have a wheel that need to be rotate in given time, how much centimeter i need to rotate in 1 sec?..

2. Relevant equations
if i have this :
Diameter = 5cm
Circumference = 15.7cm
Given time = 60sec

3. The attempt at a solution
and i got the calculation..dunno if this right/wrong..thats y i need ur help guys..=.='

Given_Times / Circumference

Answer : 3.8217 cm / sec

*/ sorry for my bad english /*

Last edited: Oct 16, 2007
2. Oct 16, 2007

### Dick

Don't you want circumference/time?

3. Oct 17, 2007

### HallsofIvy

No, he doesn't because that would have units of "time/distance". He asked "how much centimeter i need to rotate in 1 sec?" which has units of "distance/time": cm/sec.

Soharu: Yes, the circumference, in cm., divided by the time, in seconds, of one rotation will give you the speed, at the circumference, in cm/sec.

4. Oct 17, 2007

### Dick

Why do you say "circumference/time" would have units of "time/distance"?

5. Oct 17, 2007

### Jmanww

if its circumference over time then its 15.707/60 which gives .26178 cm/sec.

6. Oct 18, 2007

### soharu

thanx guys..now i got the result...my bad..my bad..it's cm/sec.
so the answer i got is same with the quote above..15.7/60 =
0.26718 cm/sec

7. Oct 18, 2007

### HallsofIvy

Because I just plain misread what you wrote, of course!