# (just joined) I need help with my pre ap precal; angular and linear velocity)

1. Feb 4, 2008

### Amaroq Zev

1.(okay just to let anyone know, I have alot of this left to do, and I don't understand much of it, like when to use certain equations and such.) pulley problem: A small pulley 6 cm in diameter is connected by a belt to a larger pulley 15cm in diameter, the small pulley is turning at 120 rpm.(from a friend I got the first two answers but I still don't understand really how to find it.)
A.) find the angular velocity of the small pulley in radians per second.= 12.566 rad/s or 4(pie) rad/s
b)find the linear velocity of the rim of the small pulley.=37.699 rad/s
c)What is the linear velocity of the rim of the large pulley? explain
d)Find the angular velocity of the large pulley in radians per second.
e)how many rpm is the large pulley turning?

2. I know that to find linear it's L=w(omega) * radius but other then that I am lost.

3. I have no real clue, at first I thought I was getting everything quite well, but I have failed miserably at it, someone aid me please.

2. Feb 4, 2008

### Amaroq Zev

(I have a lot of other problems, any help for anything...anyone...would help me so much, this is all due tomorrow...26 problems of stuff that I don't understand. Makes me feel so...icky if you will.

3. Feb 4, 2008

### Amaroq Zev

does anyone know any other online tutors or websites that help with this kind of stuff? Like pre-ap pre-calculus help?

4. Feb 4, 2008

### Amaroq Zev

(I am going to search around, see if anyone else in on right now, I am really desperate on help here...)

5. Feb 4, 2008

### Amaroq Zev

(help on the site or anything? Is anyone there? I don't know if these messages would be considered flooding but I do need help....)

6. Feb 4, 2008

### Amaroq Zev

okay, someone answer this, is the angular velocity the same when the two circles are atop of each other or when there is two seperate gears connected by a belt?

7. Feb 4, 2008

### Amaroq Zev

the pulley looks like this
_______
(o_____O) like...one large circle connected to the little one by a belt..I don't know if that helps at all...I really need help.)

8. Feb 4, 2008

### Feldoh

Your equation L=wR -- Do you know what omega is?

9. Feb 4, 2008

### Amaroq Zev

Angular velocity once found

10. Feb 4, 2008

### Amaroq Zev

(still there? sorry I was looking around, trying to learn the site...also helping another person, hopefully your there...)

11. Feb 4, 2008

### glasshut137

for A all you do is take 120 rpm and convert it to rads/sec

120 rev/min * 1min/60sec * 2(pie)/1 rev= 4 pie rad/sec

12. Feb 4, 2008

### Amaroq Zev

(Yeah I got that far, I just get confused, my teacher isn't the best descriptive teacher....um, angular velocity is to always have what unit and what does Linear supposed to have?
And how do you find the larger circle's linear and angular? Is the linear velocity the same as the smaller one?

13. Feb 4, 2008

### Amaroq Zev

(I'm not sure but I think the angular velocity is the same when the two circles are atop of one another and the linear the same when they are seperate, but again I am not completely sure, I second guess things to much. I think..)

14. Feb 4, 2008

### Amaroq Zev

Anyone there? I just have alot of questions, I know the basics, but I get it all out of order, I don't remember what belongs where and such.

15. Feb 4, 2008

### glasshut137

angular velocity would be in terms of radians/seconds while linear is in meters/second. The velocities of the larger pulley would be the same.

Sorry i can't be more descriptive i'm still trying to picture the problem so far i think that to find the angular velocity of the larger pulley you need to find its circumference. you know that the smaller pulley goes around around twice in 1 second so now you just have to find how that relates to the larger pulley.

16. Feb 4, 2008

### Amaroq Zev

(okay, this is what I know for fact, 1 revolution equals 2 (pie) radians. angular velocity is zero in the very very center of the circle, angular velocity is always in radians(I think) and linear is distance(cm,in,miles,meters) per time. I know how to do the work and such, but my answers are never right, I think my problem is that I don't gather the information out of the given info correctly, and I still don't know if the angular velocity is the same when the two circles are on top of each other or seperate, same as linear...that would clear up alot of my problems. plus I don't know how to find rpm...revolutions per minute...

17. Feb 4, 2008

### Amaroq Zev

the picture looks like that of a bicycle
_____
(o___0) thats the best I can make the picture

18. Feb 4, 2008

### Amaroq Zev

19. Feb 4, 2008

### symbolipoint

The rim velocities will be the same for each pulley because they are directly connected with a belt. Their angular velocities will be different, since they are different sizes.