Question 19N.2.HL.TZ0.b(ii)

ALTERNATIVE 1

$E_{\mathrm{T}}=\frac{1}{2}\frac{{\left(29\times {10}^{-6}\right)}^2}{18\times {10}^{-6}}+\frac{1}{2}\frac{{\left(19\times {10}^{-6}\right)}^2}{12\times {10}^{-6}}$✔

$=3.8\times {10}^{-5}«\mathrm{J}»$✔

ALTERNATIVE 2

$E_{\mathrm{T}}=\frac{1}{2}\times 18\times {10}^{-6}\times 1.6^2+\frac{1}{2}\times 12\times {10}^{-6}\times 1.6^2$ ✔

$=3.8\times {10}^{-5}«\mathrm{J}»$✔

NOTE: Allow ECF from (b)(i)
Award [2] for bald correct answer
Award [1] max as ECF to a calculation using only one charge