Conservative forces and systems


by Aniket1
Tags: conservative, forces, systems
Aniket1
Aniket1 is offline
#1
Feb9-13, 11:38 AM
P: 42
I read in a book that if the constraint forces do work, the system is conservative, else it's nonconservative. In that case, consider a system of two bodies moving in an elliptical path under gravitational attraction. Since the gravitational force is continuously doing work on the particles, by the above definition, gravitation is a nonconservative force and the system is nonconservative. However, the mechanical energy of the system remains constant and in newtonian mechanics, gravitation is classifed under conservative force. Can someone explain where am I going wrong.
Phys.Org News Partner Physics news on Phys.org
Information storage for the next generation of plastic computers
Scientists capture ultrafast snapshots of light-driven superconductivity
Progress in the fight against quantum dissipation
russ_watters
russ_watters is offline
#2
Feb9-13, 12:16 PM
Mentor
P: 21,998
Are you counting the kinetic and potential energy of the orbiting object?
Aniket1
Aniket1 is offline
#3
Feb10-13, 12:34 AM
P: 42
Yes.

WannabeNewton
WannabeNewton is online now
#4
Feb10-13, 12:40 AM
C. Spirit
Sci Advisor
Thanks
WannabeNewton's Avatar
P: 4,916

Conservative forces and systems


What book did you read this in?
mickybob
mickybob is offline
#5
Feb11-13, 05:19 AM
P: 34
Quote Quote by Aniket1 View Post
I read in a book that if the constraint forces do work, the system is conservative, else it's nonconservative. In that case, consider a system of two bodies moving in an elliptical path under gravitational attraction. Since the gravitational force is continuously doing work on the particles, by the above definition, gravitation is a nonconservative force and the system is nonconservative. However, the mechanical energy of the system remains constant and in newtonian mechanics, gravitation is classifed under conservative force. Can someone explain where am I going wrong.

Gravity is not a constraint force.

The term 'constraint force' is used to describe forces that essentially act to impose boundary conditions. An example is the reaction force of the ground on you, stopping you falling through it.

Generally these forces don't do work, since they don't act through any distance.

So the question of them being conservative or non-conservative is meaningless.


Register to reply

Related Discussions
Conservative/ Non conservative forces problem Introductory Physics Homework 1
Conservative and non-conservative systems Introductory Physics Homework 1
Problem of conservative and non-conservative forces Introductory Physics Homework 3
energy, non-conservative and conservative forces question Introductory Physics Homework 7
Conservative and non-conservative forces-problems Introductory Physics Homework 16