Gravitational Potential Energy of a satellite

Click For Summary

Discussion Overview

The discussion revolves around calculating the gravitational potential energy required to move a satellite from one circular orbit to another around the Earth. The specific scenario involves a satellite of mass 100 kg transitioning from an orbit of radius 2R to a new orbit of radius 3R, where R is the radius of the Earth. Participants explore the mathematical formulation of gravitational potential energy in this context.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Debate/contested

Main Points Raised

  • One participant presents a calculation for the gravitational potential energy in both orbits, using the formula Ui = - GMm/2(2R) for the initial orbit and Uf = - GMm/2(3R) for the final orbit, and derives an energy requirement of GMm/12R.
  • Another participant questions the inclusion of the factor of 2 in the denominators of the potential energy expressions, suggesting that the correct forms should be Ui = -GMm/2R and Uf = -GMm/3R.
  • A participant expresses skepticism regarding the textbook's inclusion of the factor of 2, indicating confusion about its correctness.
  • Another participant mentions that their own calculation yields a different energy requirement of 1.04x10^9 J, highlighting discrepancies in the results among participants.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the correct formulation of the gravitational potential energy expressions, and there is disagreement regarding the inclusion of the factor of 2 in the calculations. Multiple competing views remain regarding the correct approach to the problem.

Contextual Notes

There are unresolved questions about the accuracy of the textbook reference and the proper application of gravitational potential energy formulas. The discussion reflects uncertainty about the mathematical steps involved in the calculations.

Victorian91
Messages
18
Reaction score
0
Can someone help me..

A satellite of mass 100kg revolves round the Earth in a circular orbit of radius 2R where R is the radius of the Earth. Determine the energy needed to move the satellite to a new orbit of radius 3R.

Thanks a lot.
 
Physics news on Phys.org
Victorian91 said:
Can someone help me..

A satellite of mass 100kg revolves round the Earth in a circular orbit of radius 2R where R is the radius of the Earth. Determine the energy needed to move the satellite to a new orbit of radius 3R.

Thanks a lot.

Hi Victorian91! Welcome to PF :smile:

You have to show what you've done/tried first before we can help.
 
Okay..
This is how i did my solution to this problem..

In the old orbit, Ui = - GMm/2(2R)

In the new orbit, Uf = - GMm/2(3R)

Energy needed U = Uf -Ui

= GMm/ 12R

= 5.2X10^8 J

Is this correct?

Or it should be just putting in 2R and 3R..

Thanks..
 
Victorian91 said:
In the old orbit, Ui = - GMm/2(2R)

In the new orbit, Uf = - GMm/2(3R)
Why do you have the 2 in the denominator of each? I think you should have Ui = -GMm/2R and Uf = -GMm/3R. I'm curious why you thought the extra 2 came in.
 
Yes I agree with you..

Just that I was skeptical when my textbook included the 2(2R) and 2(3R)

That is why I post this ..

Could anyone know why?
 
I have no idea why the textbook included the extra 2. Are you sure that's exactly the problem in the book?

Also, out of curiosity, which textbook is it?
 
Well,

Its PRE - U Text STPM
Physics (Volume 1 )

Maybe a printing error..

:confused:
 
Victorian91 said:
Okay..
This is how i did my solution to this problem..

In the old orbit, Ui = - GMm/2(2R)

In the new orbit, Uf = - GMm/2(3R)

Energy needed U = Uf -Ui

That is correct but without the 2* that just seems weird, when i calculated the energy required i got an answer of 1.04x10^9J... What is the correct answer?
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
1K
  • · Replies 46 ·
2
Replies
46
Views
5K
  • · Replies 9 ·
Replies
9
Views
4K
  • · Replies 10 ·
Replies
10
Views
7K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 27 ·
Replies
27
Views
12K
  • · Replies 6 ·
Replies
6
Views
3K
  • · Replies 54 ·
2
Replies
54
Views
7K
  • · Replies 29 ·
Replies
29
Views
4K