Difference between revisions of "Talk:Atmosphere"
| Line 1: | Line 1: | ||
Drag calculation notes: | Drag calculation notes: | ||
| − | The calculation for the drag force as listed on this wiki page is incorrect. The units for the equation provided would be (Kg^2*m)/(s^2) when the unit of force (N) is Kg*m/(s^s). The equation should not include the mass of the craft as the mass of the craft has nothing to do with the amount of drag exerted on it. Remember that F=ma is a very simplified version of Newton's second law. The real way to read the equation is the sum of all instantaneous forces on a body is equal to the instantaneous mass of the body multiplied by the instantaneous acceleration of the body. It is actually more helpful to think of this drag force calculation in the context of Newton's third law. The craft is accelerating the air particles it contacts (or the pressure zone ahead of it contacts) and the equal but opposite force is applied to the craft. The mass that matters when | + | The calculation for the drag force as listed on this wiki page is incorrect. The units for the equation provided would be (Kg^2*m)/(s^2) when the unit of force (N) is Kg*m/(s^s). The equation should not include the mass of the craft as the mass of the craft has nothing to do with the amount of drag exerted on it. Remember that F=ma is a very simplified version of Newton's second law. The real way to read the equation is the sum of all instantaneous forces on a body is equal to the instantaneous mass of the body multiplied by the instantaneous acceleration of the body. It is actually more helpful to think of this drag force calculation in the context of Newton's third law. The craft is accelerating the air particles it contacts (or the pressure zone ahead of it contacts) and the equal but opposite force is applied to the craft. The mass that matters when determining aerodynamic forces is the mass of the disturbed air and this is why the density of the disturbed fluid is part of the calculation. (Before writing this I did not see the mention to this fact in the wiki page, but I am still not sure why a force would be modeled with completely wrong units. It is not to make the amount of drag be independent of the craft's mass because, as I explained above the drag equation does not consider the craft's mass. Are the internal modeling calculations all done in mass specific forces/accelerations? If so, shouldn't the true drag force then be divided by the craft's mass to yield this value? ) |
Revision as of 20:48, 15 July 2013
Drag calculation notes:
The calculation for the drag force as listed on this wiki page is incorrect. The units for the equation provided would be (Kg^2*m)/(s^2) when the unit of force (N) is Kg*m/(s^s). The equation should not include the mass of the craft as the mass of the craft has nothing to do with the amount of drag exerted on it. Remember that F=ma is a very simplified version of Newton's second law. The real way to read the equation is the sum of all instantaneous forces on a body is equal to the instantaneous mass of the body multiplied by the instantaneous acceleration of the body. It is actually more helpful to think of this drag force calculation in the context of Newton's third law. The craft is accelerating the air particles it contacts (or the pressure zone ahead of it contacts) and the equal but opposite force is applied to the craft. The mass that matters when determining aerodynamic forces is the mass of the disturbed air and this is why the density of the disturbed fluid is part of the calculation. (Before writing this I did not see the mention to this fact in the wiki page, but I am still not sure why a force would be modeled with completely wrong units. It is not to make the amount of drag be independent of the craft's mass because, as I explained above the drag equation does not consider the craft's mass. Are the internal modeling calculations all done in mass specific forces/accelerations? If so, shouldn't the true drag force then be divided by the craft's mass to yield this value? )
