Hey there! Having some difficulty with this question... is there any proportionality law between potential difference and velocity? An electric charge accelerated from rest through a potential difference of 250 V reaches a speed of 9.4 x 10^6 m/s. What speed will this same charge reach if it is accelerated by a potential difference of 125 V? So I started with conservation of energy. Ek = Ep. (.5)mv^2 = Ue = qV But how can I complete this without knowing its mass or quantity of charge? Thanks in advance!