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 Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...The Space and Astronomy Agora Two Different Distances And Masses Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response ToPosted by Richard Ruquist on January 21, 2003 12:26:36 UTC

Dear Greg,

Two of the distances in the formulas are distances between masses. The other distance is actually a change in the distance, not an actual distance. In addition there are two different masses. The mass that gets canceled out is the one being accelerated. So what you have shown is that the mass providing the force of acceleration is proportional to the acceleration times the distance between the masses squared. Newton knew that

The constant of proportionality also has units. When doing dimensional analysis, which is the name of what you have done, you have to include all units, even when they are in the constants.

Your dimensional analysis result is that the unit of mass is equal to the unit of volume, as you have said. However, that is not mathematically correct as you must always have the same units on both sides of an equation. Otherwise you cannot use the equal sign. You will learn this when you get to college.

yanniru