[单选题]
A small charged ball is accelerfp (2o;z- xmq72 oqfta8ll8qy atedth9mtl/w;ee4eln+ v - from rest to a speed v by a 500 V potential difference. If the potential difference is changed to 2000 V, what will the new spe+;9hn-w tl4vle e/t emed of the ball be?