# Circular Motion Help

1. Oct 1, 2006

### thebigeis

I am having some trouble with my physics homework.

#1) A 300m-tall tower is built on the equator. How much faster does a point at the to of the tower move than a point at the bottom?

#2) A 5m-diameter merry-go-round is initually turning with a 4.0s perio.d It slow down and stops in 20s. Before slowing, what is the speed of a child on the rim?

2. Oct 1, 2006

### thebigeis

I am having some trouble with my physics homework.

#1) A 300m-tall tower is built on the equator. How much faster does a point at the to of the tower move than a point at the bottom?

#2) A 5m-diameter merry-go-round is initually turning with a 4.0s period It slow down and stops in 20s. Before slowing, what is the speed of a child on the rim?

#3) In the Bohr model fo the hydrogen atom, an electron (mass m = 9.1X10^-31 kg) orbits a proton at a distance of 5.3X10^-11m. The proton pulls on the electron with an electric force of 8.2X10^-8N. How many revolutions per seconds does the electron make?

For #2, I just don't even know how to get the angular velocity with only the period and 5m diameter information to get the non-uniform circular motion velocity. For #3, I don't know how to derive the period (T) out of any of the information they give me. I'm new to this subject, can anyone enlighten me?

Last edited: Oct 1, 2006
3. Oct 1, 2006

### thebigeis

I just got #1.

4. Oct 1, 2006

### Integral

Staff Emeritus
For part 1, there are 2 questions you need to answer. How far does the top travel, How long does it take.

#2. What is the relationship between rotational and lineral speed?

5. Oct 1, 2006

### Chi Meson

The fact that the merry go round slows to a stop is unimportant to the question. The general principal of speed applies here. think, what is the distance covered in one revolution of a circle? (It has a name, begins with "C"). How much time does it take to complete one revolution?

6. Oct 1, 2006

### thebigeis

In one revolution fo a circle is equal to 2pi. And in the problem it says one period is 4s. And if I'm getting this straight, which I'm not, 2pi/4 would be the rev/s?

7. Oct 1, 2006

### thebigeis

I got #1, but for number 2, I don't knwo the relationship between rotational and linear speed...