- #1

trixid

- 12

- 0

I got the main problem but I can't get the rev/s.

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- Thread starter trixid
- Start date

- #1

trixid

- 12

- 0

I got the main problem but I can't get the rev/s.

- #2

Zlex

- 40

- 1

You know how many meters it will tavel in one second.

You want to change that into how many revolutions will occur in one second

Consider how many meters are in a revolution.

- #3

Physics_wiz

- 227

- 0

- #4

Physics_wiz

- 227

- 0

Hehe Zlex, we posted in the same exact minute

- #5

trixid

- 12

- 0

Ah I've got it now. Thanks a bunch.

Does 1.71 rev/s sound about right?

Does 1.71 rev/s sound about right?

Last edited:

- #6

Physics_wiz

- 227

- 0

That's not what I got, but I might have done it wrong. How did you get to that answer?

- #7

trixid

- 12

- 0

- #8

trixid

- 12

- 0

Ah! Something is horriblely wrong with what I did. The speed has nothing to do with it.

- #9

trixid

- 12

- 0

Actually, I think I'm just confusing myself. I think my answer was right...maybe?

- #10

Physics_wiz

- 227

- 0

Yep it's the circumference that's giving you the pain

- #11

HawKMX2004

- 36

- 0

Xf = Xi + ViT + 1/2aT^2

a = acceleration = 0 (constant velocity)

T = Time = 1 sec

Xf = Meter part of the speed.

Xf = 0 + 26m/s(1s)

Xf = 26 meters

So think of it this way, what percent of 47.1 is 27.6?

- #12

Physics_wiz

- 227

- 0

The problem is that the circumference is NOT 47.1 m.

- #13

HawKMX2004

- 36

- 0

- #14

Physics_wiz

- 227

- 0

He got the velocity right but the circumference he got wrong.

- #15

trixid

- 12

- 0

What's the formula for circumference?

- #16

Physics_wiz

- 227

- 0

- #17

trixid

- 12

- 0

OOPS! I was mixing up problems. I used 7.5 as r, from a different problem entirely.

I got 2.28 rev/s. I'm hoping that's right.

I got 2.28 rev/s. I'm hoping that's right.

Last edited:

- #18

Physics_wiz

- 227

- 0

You seem to be going in the right track so I'll just show you how I did it:

cintripital force = 7.75*weight of astronaut

(mv^2)/r = 7.75*mg

V^2/r = 7.75g

v^2 = 7.75gr

v = sqrt(7.75gr) = sqrt(7.75*9.98*10) = sqrt(773.45) = 27.81 m/s

circumference = 2*pi*r = 62.83 m

27.81m/s * 1circumference/62.83m = .4426 rev/s

- #19

trixid

- 12

- 0

No scratch that, it would go less than once, like your answer shows, because it doesn't go a whole revolution in one second. I think i'm catching on...slowly. This is sad, I'm confused on the part that's pretty much 8th grade math.

- #20

Physics_wiz

- 227

- 0

If it can only travel 30 m per second then it can only travel HALF the 60 m track in one second.

- #21

trixid

- 12

- 0

That's what I said, right? (Just checking to make sure I've got it.)

- #22

Physics_wiz

- 227

- 0

You got it.

- #23

trixid

- 12

- 0

Yay! Thanks a bunch.

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