Learning Goal: To practice Problem-Solving Strategy 29.1 forcharge interaction problems.
A proton and an alpha particle are momentarily at rest at adistance r from each other. They then begin to move apart. Find the speed of the proton by the time the distance between theproton and the alpha particle doubles. Both particles arepositively charged. The charge and the mass of the proton are, respectively, e and m. The e charge and the mass of the alphaparticle are, respectively, 2e and 4m.
Find the speed of the proton (vf)p by the time the distancebetween the particles doubles.
Express your answer in terms of some or all of the quantities, e, m, r, and ?0.
Which of the following quantities are unknown?

A initial separation of the particles
B final separation of the particles
C initial speed of the proton
D initial speed of the alpha particle
E final speed of the proton