The gravitational force between and around 2 objects

[robert80]

Homework Statement

These days I am having the exam for physics 1. Could you please give me the idea, howto simplify the following exercise? You have 2 spaceships of the same shape and they are from the same material. You can have circular or eliptic spaceships for instance. Now you must draw the graph how the force is changing on the straight line between the centres of gravity.

Homework Equations

The Attempt at a Solution

Its surelly not possible to look at them seperatelly and simply sum the graphs as the force in the middle of them becomes 0. And there is no zero point in the centre of the masses too. Is it possible when you calculate the gravity from 1 spaceship and solve the integrals in 1 spaceship and around 1 spaceship is than possible to transform the graph and sum both graphs, that you get zero point then? How you do that? Or is there any other way to simplify this problem? Thanks

 

[emlbiltek]

by looking the centre of mass, you can seek a solution. for the bodies are same, the centre of mass (as position) remains constant. this state, can become a reference the solving problem (momentum conservation relative to the centre of mass...).

 

[robert80]

Ok thanks, what a brilliant solution. Havent thought of that. But its true that if you take the centre of the mass coordinate system in planty of cases is very good when doing the dynamics for instance... Or rotation. Havent thought of that in this exercise.