airkyd Posted November 3, 2005 Share Posted November 3, 2005 ok , i know T^2 = k*R^2, but wat is K . cans some one explain k to me. its a real complicated one :/ Link to comment Share on other sites More sharing options...
lxxvii24 Posted November 3, 2005 Share Posted November 3, 2005 ok ' date=' i know T^2 = k*R^2, but wat is K . cans some one explain k to me. its a real complicated one :/ [/color'] my only contributioon is that , kepler's third law established this T^2 = k*R^3, tthat is all. Link to comment Share on other sites More sharing options...
5614 Posted November 3, 2005 Share Posted November 3, 2005 Indeed it is: [math]T^2 = kR^3[/math] Where: T = sideral period, R = semi-major axis & k = constant. I believe it's something like if you use sidereal period in years and astronomical units then k is 1, so it becomes just [math]T^2 = R^3[/math] Or something like that anyway! Link to comment Share on other sites More sharing options...
airkyd Posted November 3, 2005 Author Share Posted November 3, 2005 so wat is the constant , i understand the equation but i dont understand the constant bit , wat is its units , wat does it measure. i know that the constant varies for different garvitational forces. but tahts all l, Link to comment Share on other sites More sharing options...
Douglas Posted November 3, 2005 Share Posted November 3, 2005 K is defined here http://www.phy6.org/stargaze/Skepl3rd.htm Link to comment Share on other sites More sharing options...
5614 Posted November 3, 2005 Share Posted November 3, 2005 A constant is a constant. What that means is that it is always the same number (assuming you use the same units). So for example we all know e=mc^2 right, now what if I said that e=m, well that's wrong because you need to multiply m by c^2. Now we all know that c^2 will never change, it is a constant. This is what a constant is. So you could say that: 10 = k5 where k is a constant. Obviously in this case k is 2. In this example the fact that k is always the same value isn't very important as 10 and 5 are also always the same value. But say you were drawing the graph y=kx, y and x change all the time, but k is constant. What you know about the equation y=kx is that it pases through the origin (0,0) and that the gradient is k. A constant doesn't have a unit, it is just a number to make the equation work. e=m doesn't work because e would be c^2 times too small, e=mc^2 does work. No matter what value of mass or energy you use they're always related by the constant value c^2. [edit] ahh, Douglas's link just gave me the right words... for T^2 = kR^3 it means that T^2 and R^3 are proportional. They are proportional to each other by a value of k. So like T^2 = R^3 is false because you need to multiply the R^3 value by k first... k is always the same number, no matter value of T or R you put in. Link to comment Share on other sites More sharing options...
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