Đáp án:
\(\begin{array}{l}a)\left| q \right| = \dfrac{8}{3}{.10^{ - 9}}C\\b){r_2} = 1,6cm\end{array}\)
Giải thích các bước giải:
a)
\(\begin{array}{l}F = k\dfrac{{\left| {{q^2}} \right|}}{{{r^2}}} \Leftrightarrow 1,{6.10^{ - 4}} = {9.10^9}\dfrac{{{q^2}}}{{0,{{02}^2}}}\\ \Rightarrow \left| q \right| = \dfrac{8}{3}{.10^{ - 9}}C\end{array}\)
b)
\(\begin{array}{l}{F_2} = k\dfrac{{{q^2}}}{{r_2^2}}\\ \Rightarrow {r_2} = \sqrt {k\dfrac{{{q^2}}}{{{F_2}}}} = \sqrt {{{9.10}^9}\dfrac{{{{\left( {\dfrac{8}{3}{{.10}^{ - 9}}} \right)}^2}}}{{2,{{5.10}^{ - 4}}}}} = 0,016m = 1,6cm\end{array}\)