The equation widely used to calculate the force on a projectile in an electromagnetic launcher, more specifically a railgun, is: F = 0.5 * L' * I^2 where: --> F is the force in newtons --> L-prime is the inductance gradient of the rails in henries/meter (H/m) --> and I is the current through the rails in amperes. How would I calculate or estimate the inductance of a given pair of rails? FYI, they are 0.0625 inches wide, 6.0 inches long and 0.25 inches high, being separated by 0.125 inches. I have had only a brief introduction to calculus, therefore I'm not entirely sure what to do with the "L-prime" factor, which is measured in henries/meter. I know that inductance is measured in henries. Would I simply take the total inductance of the rails, in henries, and divide this by the length of the rails, in meters? If so, why is the considered "prime?" It seems that I remember when something was prime we applied the "power rule" to it, in my former calculus class, that is. Any help would be GREATLY appreciated. Thanks in advance for your time.