a 5.0-nF parallel plate capacitor with a sheet of Mylar (k = 3.1) filling the space between the plates is charged to a potential difference of 130 V and then disconnected. How Much work is required to completely remove the sheet of Mylar from the space between the two plates?

Question

a 5.0-nF parallel plate capacitor with a sheet of Mylar (k = 3.1) filling the space between the plates is charged to a potential difference of 130 V and then disconnected.  How Much work is required to completely remove the sheet of Mylar from the space between the two plates?

anonymous · Answer

So I thought $$\Delta U = U_f - U_i $$ where $$U_i = CV^2/2 $$ is with the 5.0nF C and 130V, and the final energy is the same equation except C is the capacitance divided by the dielectric constant 3.1.

I got the order of magnitude right (x10^-5) but not the numbers.

Any thoughts?