# Homework Help: Linear velocity at equator with respect to the sun

1. Feb 6, 2010

### deathcap00

1. The problem statement, all variables and given/known data

What is the linear velocity of a persion standing at the Earth’s equator with respect to the Sun, when the Sun is just at the Eastern horizon?

2. Relevant equations

Not sure, I used to v=d/t to solve for a person's linear velocity at the equator, just not sure how to handle the "with respect to" portion and how to use the "eastern horizon" information to help shape a solution.

2. Feb 6, 2010

### deathcap00

Do I consider the earth a particle circling the sun first or something?

3. Feb 7, 2010

### deathcap00

does anyone have any suggestions on this one? I can't see to figure it out, thanks all.

4. Feb 7, 2010

### dr_k

Although the problem mentions "linear velocity", this is a circular motion problem. A person standing on the Equator has a tangential velocity relative to the center of the Earth, and it also has a tangential velocity relative to the center of the Sun. It may turn out that the "speed", or magnitude, of one of these tangential velocities is negligible when compared to the other, but you must run the numbers through to see. Step #1, for you, is to draw a picture. I'll get you started:

http://img246.imageshack.us/img246/4949/earthsun.jpg [Broken]

n.b. Picture is not to scale, $\rm \frac{R_E}{1 AU} \sim 1~x~10^{-5}$

Last edited by a moderator: May 4, 2017