Creating an Electromagnet

I'm part of a design group for a university design course and we need to launch a mass using the solenoid idea (iron rod wrapped with wire). The problem that I am having is calculating the force produced by the electromagnet given a certain voltage and current.

I know that F=q(v x B)
in this equation we are assuming that the field is perpendicular so what we have is just F=qvB
What I need is an expression that gives the force produced by the electromagnet as a function of variables that I can find, such as voltage, current....

In the above equation, I'm trying to find the force but I do not know what v is and q. q is the charge but how do I measure that? Any help would be beneficial.
I already tried sources on wikipedia and on hyperphysics. I need to know how to solve for the charge of the electromagnet and the velocity.


Science Advisor
Homework Helper
F=q(v x B) isn't really appropriate for an electronmagnet

For a solenoidm, the force on the core is
Force = B^2 A / 2 mu_0

where, B = mu_relative * number of turns * current / length
I forgot to mention that the mass being launched is .02 kilograms. If capacitors were to be used, how would they help? The mass needs to be launched a distance of 6 to 10 meters. Another requirement is that the power supply can not be no more than 24 volts. What we are using is a 18.8 V rechargeable drill battery.

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