Question

If you use 17 J of work to push a charge into an electric field and then release the charge, as the charge flies past its starting position, its kinetic energy is

Answer 1

Static electric field is conservative field, so work, done by the field when particle’s trajectory is closed, equal to 0 (start and end point the same).
This means that due to Law of Conservation of energy, kinetic energy of particle will be equal to energy we used to put particle into the field.