FORMULAS Fun fact is we have learned a bunch of the formulas needed to make sure you stay safe while building the machines of tomorrow in our physics class this semester! ​ This one is used to calculate the magnetic field on a long straight wire or the rails of the gun.  The first set of terms are a constant so no need to go hunting for numbers to put in.  The second part though you do need some numbers for your specific system.  You will need the radius of the wire and how much current you have going through your system. ​ ​ Here we can use the magnetic field calculation, the current being delivered, and the length of our rails to get the magnitude of the force for our projectile. Now these two can give you a rough idea of what you are looking for, but as always a more accurate result needs some integration, inductance values, resistance values, and to help you out a computer simulation for the precise answers. However, if you want to run through a few on your own here they are:  Here we can calculate the resistance and inductance as the projectile is traveling down the barrel. Obviously we want to know the velocity of the projectile as it moves down and out. Then lumping some of our things together we can get the overall force.