Universal gravitation: mass of 2 objects

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Homework Help Overview

The problem involves two objects attracting each other with a specified gravitational force and total mass, prompting participants to determine the individual masses of the objects. The context is within the subject area of universal gravitation.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the relationship between the masses and the total mass, with one suggesting the mass of one object could be expressed in terms of the other. There is uncertainty about whether the masses are equal and how to set up the equations correctly.

Discussion Status

The discussion is active, with participants exploring different interpretations of the problem. Some guidance has been provided regarding the need for a second equation to relate the two masses, and there is a collaborative effort to clarify the setup.

Contextual Notes

Participants note the lack of explicit information about the equality of the masses, which influences their approach to the problem. The total mass constraint is emphasized as a key factor in their reasoning.

mickellowery
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Homework Statement


Two objects attract each other with a gravitational magnitude 1.00x10-8N when separated by 20.0cm. If the total mass of the two objects is 5.00kg what is the mass of each?


Homework Equations


Fg=G*m1m2/r2
G=6.673x10-11Nm2/kg2
I'm not real sure how to go about this one since they don't say whether or not the two masses are equal. The answers turn out to not be equal which killed my idea of how to set this up. I was going to try making one of the masses 5/2 and solving for the other mass but this just gives me half of the total mass.

The Attempt at a Solution

 
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If the mass of one of the objects was 'm', what would be the mass of the other?
 
Thats a great question Doc. Would it just be m/2? I'm not very sure.
 
mickellowery said:
Would it just be m/2? I'm not very sure.
No guessing. Figure it out. Hint: What's the total mass?

Here's how to look at it. You've already called the masses m1 and m2. That's perfectly fine. You already have one equation: Newton's law of gravity. But since you have two unknowns, you'll need a second equation. Hint: m1 + m2 = ??
 
Oh OK so then it would be m1=5-m2. Then I would sub in 5-m2 for m1
 
Yep. Then you'd solve for m2 (and then for m1).
 
Alrighty thanks much for helping a nearly lost cause in physics.
 

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