Bjarne Posted September 26, 2013 Share Posted September 26, 2013 So soon the moon moves between the Sun and the Earth, by eclipse, - and the 3 objects will be aligned, - how fast can the Earth possible accelerate due to that ? And how can it be calculated ? Link to comment Share on other sites More sharing options...
swansont Posted September 26, 2013 Share Posted September 26, 2013 Newton's law of gravitation should suffice. Link to comment Share on other sites More sharing options...
Bjarne Posted September 26, 2013 Author Share Posted September 26, 2013 Newton's law of gravitation should suffice. Is it so simple that I only need to add the acceleration due to gravity of the Moon (based on MG/r^2) 7,35E22*6,67@E-11/384000000^2 = 0,000033 m/s^2 I think not, it must be calculated from the common gravitational centre (near the center of the Sun) right =? Link to comment Share on other sites More sharing options...
swansont Posted September 26, 2013 Share Posted September 26, 2013 It's a vector, so the two contributions add as vectors. Link to comment Share on other sites More sharing options...
Strange Posted September 26, 2013 Share Posted September 26, 2013 In fact, it seems to be the easiest point in time to calculate the combined effect of the two on the Earth as the two vectors will be aligned so you can simply add the two forces. At any other point, you will have to take into account the angle between the two vectors. Link to comment Share on other sites More sharing options...
imatfaal Posted September 27, 2013 Share Posted September 27, 2013 In fact, it seems to be the easiest point in time to calculate the combined effect of the two on the Earth as the two vectors will be aligned so you can simply add the two forces. At any other point, you will have to take into account the angle between the two vectors. One of the two easiest places 1 Link to comment Share on other sites More sharing options...
Strange Posted September 27, 2013 Share Posted September 27, 2013 One of the two easiest places Unless you find subtraction harder than addition. 1 Link to comment Share on other sites More sharing options...
Janus Posted September 27, 2013 Share Posted September 27, 2013 (edited) Unless you find subtraction harder than addition. In which case you can just convert to 10's complement and subtract by adding. Edited September 27, 2013 by Janus 1 Link to comment Share on other sites More sharing options...
Ophiolite Posted September 30, 2013 Share Posted September 30, 2013 The division on this point seems to have multiplied the responses. 2 Link to comment Share on other sites More sharing options...
michel123456 Posted September 30, 2013 Share Posted September 30, 2013 IIRC an eclipse is not seen as such from everywhere on the globe. In order to get perfect alignment you need a very specific eclipse. And IIRC it is the Earth-Moon system that is orbiting the Sun, anyway. You can call me IIRC. Link to comment Share on other sites More sharing options...
Bjarne Posted December 31, 2013 Author Share Posted December 31, 2013 (edited) In fact, it seems to be the easiest point in time to calculate the combined effect of the two on the Earth as the two vectors will be aligned so you can simply add the two forces. At any other point, you will have to take into account the angle between the two vectors. Let’s say that the angle from a point between the Earth and Moon is 90 degree, - and the angle from the same point on Earth to the Sun zero degree. To keep it simple let’s say that the acceleration due to gravity against the Sun and the Moon is the same acceleration What still confuses me is that according to Newton’s second law (so far as I understand it) the resulting force will point between the two forces, which only mean only change of direction and therefore no change of force acting on the Earth so far. On the other hand there is no doubt that so soon the Eaeth/Moon/Sun alignment is completed (total eclipse) then 2 forces must have united , and therefore double so strong But where does the unification of the 2 forces start ? Does the 2 force already start to unite after the angle between the 2 forces (Sun and Moon) begins to decrease to less as 90 degree relative to a point on Earth? Or first when the eclipse starts ? I am lost Edited December 31, 2013 by Bjarne Link to comment Share on other sites More sharing options...
swansont Posted December 31, 2013 Share Posted December 31, 2013 Let’s say that the angle from a point between the Earth and Moon is 90 degree, - and the angle from the same point on Earth to the Sun zero degree. To keep it simple let’s say that the acceleration due to gravity against the Sun and the Moon is the same What still confuses me is that according to Newton’s second law (so far as I understand it) the resulting force will point between the two forces, which only mean only change of direction and therefore still the same That's not how you add vectors. The resultant at 90 degrees will follow the Pythagorean theorem. c2 = a2 + b2 0.000042 in this case. Link to comment Share on other sites More sharing options...
Bjarne Posted December 31, 2013 Author Share Posted December 31, 2013 That's not how you add vectors. The resultant at 90 degrees will follow the Pythagorean theorem. c2 = a2 + b2 0.000042 in this case. Thank you what then is the angle is 45 degree and 10 degree ? Link to comment Share on other sites More sharing options...
swansont Posted December 31, 2013 Share Posted December 31, 2013 http://www.mathwarehouse.com/vectors/resultant-vector.php Link to comment Share on other sites More sharing options...
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