# faq10 - FREQUENTLY ASKED QUESTIONS February 20, 2012...

This preview shows pages 1–2. Sign up to view the full content.

This preview has intentionally blurred sections. Sign up to view the full version.

View Full Document
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: FREQUENTLY ASKED QUESTIONS February 20, 2012 Content Questions How do you find the center of mass? The position of the center of mass of a system of N masses is given by ∑ N i =1 m i ~ r i M , where ~ r i are the positions of the masses with respect to some origin. It’s kind of the “average position” of the masses. For two masses A and B , taking the origin as the position of A and the x axis along the line between the masses, the CM is at position x CM = m A x A + m B x B m A + m B = m B x B m A + m B . Now in our notation from class a A = x CM == m B x B m A + m B , and a B = x B- a A , which works out to a B = m A x B ma A + m B , and we get a B /a A = m A /m B . For the Doppler shift, what is the “plane of the sky”? If you imagine the celestial sphere as infinitely far away, a piece of its surface is flat. That’s the plane you are looking at when you look at an object. The angle of inclination i is the angle between that plane and the plane of the orbit: if the orbit is face-on, its plane is perpendicular to the line of sight...
View Full Document

## This note was uploaded on 02/26/2012 for the course PHYSICS 105 taught by Professor Kruse,m during the Spring '08 term at Duke.

### Page1 / 2

faq10 - FREQUENTLY ASKED QUESTIONS February 20, 2012...

This preview shows document pages 1 - 2. Sign up to view the full document.

View Full Document
Ask a homework question - tutors are online