Rail gun with non-constant acceleration energy problem

[pat666]

Homework Statement

attached

Homework Equations

The Attempt at a Solution

I think i need to use energy methods for this because the acceleration is not constant..
trouble is I don't know the formula for the potential energy in cases like this.

Thanks for any help.

 

[Redbelly98]

What's the force on a current-carrying wire in a magnetic field? (There is a formula for it.)

 

[pat666]

F=BIL that's how i found the acceleration.. but i don't see how that helps with b??

 

[Jokerhelper]

how was this current produced in the first place? What kind of current are you dealing with?

 

[pat666]

I don't know what you mean? it was supplied by a cap if that helps?