Question

Two particles have equal masses of 5.0 g each and opposite charges of $+4\times {10}^{-5}C$ and $-4\times {10}^{-5}C$. They are released with a separation of 1.0 m between them. Find the speeds of the particles when the separation is reduced to 50 cm.

Answer 1

Applying conservation of momentum by initial and final stage
$P_i=0P_f=m{v}_1+m{v}_2{P}_f=P_i{v}_1=-v_2...\left(1\right)$
Now applying energy conservation by two points
$K{E}_i+(P.E{)}_i=K{E}_f+(P.E{)}_f$
$\frac{m{v}_1^2-m{v}_1^2}{2}=k{q}^2(\frac{2}{r}-\frac{1}{r})$
$m{v}_1^2=\frac{154}{10}$
$v_1=53.66m/s=-v_2$.