--- Quote from: rsterne on June 11, 2014, 01:46:48 PM ---First of all, let me state that using the current International Standard (2008) for the value of "g" (the acceleration due to gravity), which is 32.1740 ft/s^2, the correct divisor in the formula is 7000 x 2 x 32.174 = 450436.... However, the value of "g" varies from about 32.08 at the equator to 32.26 at the poles, due to the increase in circumference of the Earth at the equator due to centrifugal force.... Over the years, this has meant that the definition of one "g" has changed....
Physics texts when I attended University used g = 32.16 ft/sec ^2.... and that agrees exactly with the value of 450240.... It has been revised through more accurate measurement to 32.174.... Therefore, one could, tongue in cheek, say that the value of the divisor depends on your age.... and in fact the commonly used value was likely correct at the time.... The difference in the two is 0.04%, which for an airgun putting out 50 FPE is an error of only 0.02 FPE.... Since we can only measure the velocity within 1 fps (quoting it to 0.1 fps as is often done is ludicrous when the Chronys have a resolution of only about 1%), and using conventional attention to significant figures (three for the velocity means three for the energy).... at best we should never quote FPE to better than 1 decimal point.... The same applies to the pellet weight, measuring to less than 0.1 gr. is useless as the pellets vary more than that.... With a 25 gr. pellet, 0.1 gr is 0.4%, which is 10 times the error in the divisor.... Therefore, the difference between using 450240 and 450436 is about 1/5th of the accuracy we can attain when measuring the velocity to 1 fps and about 1/10th of the accuracy of the bullet weight to 0.1 gr....
While the correct value of the divisor in the equation is 450436, using the current, widely publicized 450240 produces errors an order of magnitude less than other errors in our measurements.... In other words, 450240 isn't correct, but it doesn't matter....
CK
