A proton and an alpha particle are momentarily at rest at a distance y from each other. They then
begin to move apart. Find the speed of the proton
by the time the distance between the proton and
the alpha particle doubles.
Both particles are positively charged. The charge
and the mass of the proton are, respectively, e and
m. The charge and the mass of the alpha particle
are, respectively, 2e and 4m.
Find the speed of the proton (Ur )p by the time the distance between the particles doubles. Express your answer in terms of some or all of the quantities e, m, r, and ε.