A question is already asked ( How does this “simple” electric train work? ). But I've got a question about it.
In order to calculate the force which is being exerted on the system including magnets and battery, should we use Lorentz force equation?
If yes, which form should we use, $$F=q(E+V\times B)$$
Or $$F=q(V\times B) = I(L\times B)$$
