a ball of mass 2 kg and charge 1uC is dropped from the top of a tower.in space electric field exist in horizontal direction away from the tower which varies as E=(5-2x) *10^6 .find the maximum horizontal distance ball can go..

Find the horizontal force by E*q and divide it by mass to get horizontal acceleration.
now you''ll have expression for horizontal variable accelertaion.
integrate it twice w.r.t. x and equate it to zero.you will get the value of max. distance.