1. The problem statement, all variables and given/known data What potential difference is needed to accelerate a He + ion (charge +e, mass 4 u) from rest to a speed of 2.0 * 10^6 m/s? 2. Relevant equations Kf + Uf = Ki + Ui U = qV where V is potential difference (volts) K = (1/2)mv^2 3. The attempt at a solution I chose the rest point to be r = 0, so even with U = Kq_1q_2/r, it would equal zero at the start. Then: (1/2)mv^2 = -qV V = (-1/2q)mv^2 = -(2q/)uv^2 m = u* 1.66*10^-27 kg/u = 1.66*10^-27 kg V = -(2/(1.6*10^-19 Coulombs)) * (1.66*10^-27 kg)(2.0*10^6 m/s)^2 = -83000 volts Is this right?