Orbital Period of Apollo Mission

Click For Summary

Homework Help Overview

The discussion revolves around calculating the orbital period of a command module during the Apollo missions, specifically in a low circular orbit above the Moon. The problem involves parameters such as the average height above the Moon's surface and the Moon's radius, along with its mass and the gravitational constant.

Discussion Character

  • Mathematical reasoning, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the calculation of the orbital period using the provided formula and parameters. There is a focus on unit conversion, particularly the radius of the Moon and the implications of using kilometers instead of meters. Questions arise regarding the expected units of the final answer and the validity of the given answer in the worksheet.

Discussion Status

Participants are actively engaging with the problem, with some clarifying assumptions and recalculating based on different interpretations of the radius. There is acknowledgment of potential errors in unit conversion and the implications for the final result. While some participants express confusion, others provide insights that guide the discussion toward understanding the calculations better.

Contextual Notes

There is a noted discrepancy between the calculated results and the answer provided in the worksheet, leading to discussions about possible typos in the problem statement. Participants are also considering the implications of using different values for the Moon's radius.

Immy2000
Messages
8
Reaction score
0

Homework Statement



On each of the apollo missions the command module was placed in a very low aprox circular orbit above the moon. Assum the avrg hieght was 60km above surface of moon and moons radius is 7738km. (Mass of moon=7.34x10^22kg)

What was the command modules orbital period?

M=7.34x10^22kg
r=7738+60
G=6.67x10^-11

Homework Equations



t^2=4pi^2r^3/GM(source)

The Attempt at a Solution



T^2=4pi^2(7738+60)^3 / (6.67x10^-11)(7.34x10^22)

T^2= (1.87...x10^13) / (4.89...x10^12)

T^2= 3.8237...

T=Square Root(ANS)

T= (1.9554.. Days x 24 Hours) = (46.93.. Hours)

But the back of my worksheet says the answer is 17.2 hours or 6.18x10^4 seconds

GAH I am so confused! >_< Your help is much appreciated!
 
Physics news on Phys.org
Isn't the radius of the moon 1,738 km?
 
Yeah it is but I am assuming I am supposed to use what the question gives me.. let me redo the calculation with 1738km's though...

Alright so I get to the part where you have to square root T^2 and I get 0.21649... days (I think) and if I multiply that by 24, I should get hours, but when I do so I get 5.19...which is off from 17.2 hours..JEEZ I think I made a really silly mistake. Radius is in "m" right? I plugged in Km! Oh my!

Yeppers, it was the conversion. Wow. Please Lock or Delete this thread. :)
 
Last edited:
Why do you think the result of the calculation will be in days?
If you use the quantities in SI units, the period will be in seconds.
Then you can convert in hours, of course.
The answer is around 1.8 hours.
 
Yeah I later realized it was in seconds but as far as the answer goes, its 17.2 hours. Thanks for the help guys! :)
 
If you take the radius 7738 then you get something close to 17 hours. But I thought this value is just a typo. This will mean the Moon is bigger than Earth...
 
I know its quite silly however the answer was calculated with that number. Therefore I assume that it was typoed and then answered, then printed and handed out to the students.
 

Similar threads

Kepler's law of periods problems about orbiting satellite
  • · Replies 7 ·
Replies
7
Views
4K
What Is the Orbital Period of a Satellite at 1000 km Altitude?
  • · Replies 5 ·
Replies
5
Views
3K
Find Density Given Period of Orbit
  • · Replies 12 ·
Replies
12
Views
6K
How Long and Fast Did Apollo 11 Orbit the Moon?
  • · Replies 1 ·
Replies
1
Views
6K
Moon Orbit Period Calc: Equatorial Radius of Earth & Time
  • · Replies 18 ·
Replies
18
Views
3K
What is the period of the ISS orbit?
  • · Replies 2 ·
Replies
2
Views
3K
Universal gravitation 6-determine strength of gravitational field
  • · Replies 3 ·
Replies
3
Views
2K
Issues with Apollo 11 TLI Simulation – Discrepancies in Return Orbit
  • · Replies 3 ·
Replies
3
Views
2K
Solving Physics Time Problem: Apollo Lunar Landing Mission
  • · Replies 1 ·
Replies
1
Views
2K
How Long Does It Take to Orbit the Moon at an Altitude of 100km?
  • · Replies 4 ·
Replies
4
Views
2K