Calculating Mass of Identical Lead Spheres Attracting 0.30(myu)N

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    Gravity Universal
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Homework Help Overview

The problem involves calculating the mass of two identical lead spheres that attract each other with a specified force at a given distance apart. The context is rooted in gravitational force and involves the application of Newton's law of universal gravitation.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the application of the gravitational force equation and question the use of units in the problem. There are attempts to manipulate the equation to isolate variables, and some participants express uncertainty about the correct approach to take.

Discussion Status

The discussion is ongoing, with participants providing feedback on each other's understanding of the problem. Some guidance has been offered regarding the interpretation of units and the relationship between the masses of the spheres, but there is no clear consensus on the next steps to take.

Contextual Notes

There is confusion regarding the use of units and the implications of gravitational force in the context of the problem. Participants are also navigating the assumptions about the identical nature of the spheres and how that affects their calculations.

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Homework Statement



Two identical lead spheres are 14cm apart and attract each other with a force of 0.30(myu)N .

What is their mass?

Homework Equations



F = GMm/r^2


The Attempt at a Solution



not sure but :

let myu = u.

.3uN = GMm/r^2

.3umg = GMm/r^2

u = 10/3 *GM/(r^2*g)


not sure what to do next.

Do I use the same equation for sphere 2, but solve for M and substitute?
 
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You are confused. N means Newtons - it is not a number, it is a unit - it is a standard measurement for force, kind of like centimeters is for length. mg is the force of gravity (on EARTH, which has nothing to do with the problem!), and is not a unit.

This problem is really just plug and chug. You know that the two balls are identical, so that m = M. Otherwise, you're given all the data you need. You don't seem to understand the equation or the concept. Before you manipulate equations, be sure to have an intuitive feel for what the equation actually means.
 
how about this :

Fg1 = G*M2 / r2

so,

.30u = G*M2 / r2

and just solve for M?
 
help, anyone?
 

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