Question

Two electrons are moving towards each other, each with a velocity of $10^{6} m / s$. What will be closest distance of approach between them?

• A. $1.53 \times 10^{-8} m$
• B. $2.53 \times 10^{-10} m$
• C. $2.53 \times 10^{-6} m$
• D. Zero

Answer 1

Answer: (B)

$\frac{1}{2}\left(9.1 \times 10^{-31}\right)\left(10^{6}\right)^{2}$
$=\frac{9 \times 10^{9} \times\left(1.6 \times 10^{-19}\right)^{2}}{r}$
$9.1 \times 10^{-19}=\frac{9 \times 10^{9} \times 2.56 \times 10^{-38}}{r} $
$r=2.56 \times 10^{-10}\, m$