\(=\left(\frac{\varepsilon}{ R }\right) \ell B =\left(\frac{ vB \ell}{ R }\right) \ell B =\frac{ vB ^2 \ell^2}{ R }=\frac{4}{5} \times\left(\frac{15}{100}\right)^2 \times 1^2\)
\(=\frac{4}{5} \times \frac{225}{10^4}\)
\(=\frac{180}{10^4}=0.018\,N\)
\(=18 \times 10^{-3}\,N\)