Loading in 5 sec....

Physics of Astronomy, week 4, winter 2004 Astrophysics Ch.2PowerPoint Presentation

Physics of Astronomy, week 4, winter 2004 Astrophysics Ch.2

- By
**mitch** - Follow User

- 52 Views
- Uploaded on

Download Presentation
## PowerPoint Slideshow about ' Physics of Astronomy, week 4, winter 2004 Astrophysics Ch.2' - mitch

**An Image/Link below is provided (as is) to download presentation**

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.

- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript

Physics of Astronomy, week 4, winter 2004Astrophysics Ch.2

Star Date

Ch.2.1: Ellipses (Matt #2.1, Zita #2.2)

Ch.2.2: Shell Theorem

Ch.2.3: Angular momentum (J+J, #2.7)

#2.11: Halley’s comet

Learning plan for week 5

Ch.2.1: Ellipses (Matt #2.1, Zita #2.2)

Make an ellipse: length of string between two foci is always r’ + r = 2a.

Eccentricity e = fraction of a from center to focus.

#2.1: Derive the equation for an ellipse.

Distance from each focus to any point P on ellipse:

r2=y2+(x-ae)2 r’2=y2+(x+ae)2

Combine with r+r’=2a and b2 = a2(1-e2) to get

Ch.2.2: Shell Theorem (p.36-38)

The force exerted by a spherically symmetric shell acts as if its mass were located entirely at its center.

The force exerted by the ring of mass dMring on the point mass m is

Where s cosf = r - R cos q and s2 = (r - R cos q )2 + (R sin q )2 and

dMring = r(R) dVring and

dVring = 2 p R sinq R dq dR

Substitute this into dF and integrate

Change the variable to u = s2 = r 2 + R 2 - 2rR cos q. Solve for

cos q =

sin q =

Substitute these in and integrate over du to get

Density = mass of shell / volume of shell

r(R) = dMshell / dVshell

So dMshell = r(R) dVshell = 4 p R2r(R) dR

Which is the integrand of

So the force on m due to a spherically symmetric mass shell of dMshell:

The shell acts gravitationally as if its mass were located entirely at its center.. Finally, integrating over the mass shells, we find that the force exerted on m by an extended, spherically symmetric mass distribution is

F = GmM/r2

Center of Mass reference frame

Total mass = M = m1+ m2

Reduced mass = m

Total angular momentum L=m r v = m rp vp

Virial Theorem

<E> = <U>/2

where <f> = average value of f over one period

Example: For gravitationally bound systems in equilibrium, the total energy is always one-half of the potential energy.

Learning Plan for week 5 (HW due Mon.9.Feb):

Mon.2.Feb: Introduction to Astrophysics Ch.3

Universe Ch.5.1-3, #6, 11 (Jared + Tristen)

Universe Ch.5.4-5, #25 (Brian + Jenni)

Universe Ch.5.6-8, #27, 29 (Erin + Joey)

Universe Ch.5.9, #34, 36 (Matt + Chelsea)

Universe Ch.19.1, #25 (Annie + Mary)

Tues.3.Feb: HW due on Physics Ch.6

Universe Ch.19.2-3, #34, 35 (Jared + Tristen)

Universe Ch.19.4-5, Spectra -> T,Z, #43 (Erin + Joey)

Universe Ch.19.6, L(R,T), #46, 50 (Annie + Mary)

Universe Ch.19.7,8, HR, #52 (Brian + Jenni)

Thus.5.Feb: HW due on Astrophysics (CO) Ch.2

CO 3.1, Parallax, #3.1 (Jared + Tristen)

CO 3.2, Magnitude, #3.8 (a-d) (Erin + Joey)

CO 3.3 Wave nature of light, #3.6 (Matt + Chelsea)

CO 3.4, Radiation, #3.8 (e-g) (Brian + Jenni)

CO 3.6, Color index, #3.13 (Annie + Mary)

Download Presentation

Connecting to Server..