An alpha particle (the nucleus of a helium atom, with charge +2e and a mass four times that of a proton) and an antiproton (which has the same mass as a proton but charge -e) are released from rest a great distance apart. They are oppositely charged , so each accelerates toward the other. What are the speeds of the two particles when they are 2.5 nm apart?
HINT: You'll need to use two conservation laws. And what does "a great distance" suggest about the initial value of r?