• Support PF! Buy your school textbooks, materials and every day products via PF Here!

Negative M.E.

  • Thread starter ritwik06
  • Start date
580
0
What is the significance of negative mechanical eneregy of a body?
Eg. electron in 1st orbit of H atom
 

Mapes

Science Advisor
Homework Helper
Gold Member
2,592
17
It just means that the reference energy level (the "zero") is taken at a higher level. In this case, the reference is conventionally taken to be an electron at an infinite distance from the nucleus.
 

dynamicsolo

Homework Helper
1,648
4
In describing the total mechanical energy of a system, a negative value is interpreted as meaning that the system is bound; that is to say, the total kinetic energy of all the particles (which is non-negative) has a smaller magnitude than the total potential energy of the fields between them. So there is not enough kinetic energy for members of the system to separate to limitless distances.

An example is the total mechanical energy for a satellite in, say, a circular orbit around a planet. If the masses of satellite and planet are m and M>>m, respectively, and the radius of the orbit is R, then the kinetic energy of the satellite is

(1/2)·m·(v^2) = GmM/2R ,

while the gravitational potential energy of the field is

-GmM/R .

Thus, the total mechanical energy for the system is

-GmM/2R .

(We are treating the mass of the planet as effectively infinite here for simplicity. We really should use "reduced mass" for the system.)

A similar result is found for other sorts of systems bound by forces which can be described by potential functions.
 
580
0
Thanks a lot. I have understood it quite right. thanks for the help once agin.
 

Related Threads for: Negative M.E.

  • Posted
Replies
3
Views
17K
  • Posted
Replies
4
Views
1K
  • Posted
Replies
7
Views
2K
  • Posted
Replies
4
Views
420
  • Posted
Replies
1
Views
5K
  • Posted
Replies
1
Views
1K
  • Posted
Replies
3
Views
2K
  • Posted
Replies
5
Views
1K

Physics Forums Values

We Value Quality
• Topics based on mainstream science
• Proper English grammar and spelling
We Value Civility
• Positive and compassionate attitudes
• Patience while debating
We Value Productivity
• Disciplined to remain on-topic
• Recognition of own weaknesses
• Solo and co-op problem solving
Top