Conceptual Question: Stars in intergalactic space with speed

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Homework Help Overview

The discussion revolves around the motion of stars in intergalactic space, specifically addressing how their speed and acceleration change as they move apart. Participants are exploring concepts related to gravitational attraction and the implications of Kepler's and Newton's laws.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are questioning the relationship between distance, speed, and acceleration in the context of gravitational forces. There is an exploration of whether the speed should increase or decrease as stars move apart, and how this relates to the forces acting on them.

Discussion Status

Some participants are beginning to clarify their understanding of the difference between speed and acceleration, while others are still grappling with the implications of gravitational forces on the motion of the stars. There is a mix of interpretations and attempts to reconcile the concepts presented.

Contextual Notes

Participants are discussing the effects of gravitational force as distance increases, with some uncertainty about the application of Newton's and Kepler's laws in this scenario. The conversation reflects a need for deeper exploration of these fundamental concepts.

idllotsaroms
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Homework Statement



http://postimage.org/image/7rgmo1527/
How is the speed decreasing and acceleration decreasing in this problem?

Homework Equations



Kepler's Laws?


The Attempt at a Solution



I remember in lecture my professor was saying something along the lines of objects attracting each other. So, since there are two stars that are maybe attracting each other, as they get farther and farther apart by a distance of r, shouldn't the speed increase--because the force of attraction (already negligible) is even smaller as they go farther apart? Does this question pertain to Newton's laws or Kepler's laws?

Thank you for your time!
 
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idllotsaroms said:

Homework Statement



http://postimage.org/image/7rgmo1527/
How is the speed decreasing and acceleration decreasing in this problem?

Homework Equations



Kepler's Laws?

The Attempt at a Solution



I remember in lecture my professor was saying something along the lines of objects attracting each other. So, since there are two stars that are maybe attracting each other, as they get farther and farther apart by a distance of r, shouldn't the speed increase--because the force of attraction (already negligible) is even smaller as they go farther apart? Does this question pertain to Newton's laws or Kepler's laws?

Thank you for your time!
Do you know the difference between acceleration and speed?
 
mm speed is a scalar and acceleration is vector? Acceleration of the rate of change of the speed.
 
idllotsaroms said:
mm speed is a scalar and acceleration is vector? Acceleration of the rate of change of the speed.
So the speed can be decreasing but at an ever slower rate of decrease, Right?
 
Right that would explain the acceleration decreasing, sorry I understood that part already, (even thought I said "and acceleration decreasing") but am having a difficult time understanding how the speed is decreasing.
 
What force is acting on each star? Is that force directed in the same direction as their motion or not?
 
Okay, I think I understand it now, its like if a person was on the surface of the Earth and as they got farther and farther away their speed would decrease because the force of gravity (which is the only force acting on the stars) would diminish and the person would go slower and slower as he got farther and farther away (decrease in acceleration)

Thanks! SammyS and Phinds
 
idllotsaroms said:
Okay, I think I understand it now, its like if a person was on the surface of the Earth and as they got farther and farther away their speed would decrease because the force of gravity (which is the only force acting on the stars) would diminish and the person would go slower and slower as he got farther and farther away (decrease in acceleration)

Thanks! SammyS and Phinds

No, I don't thing you are thinking this through properly.
 

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