Electric field lines can never cross. What would crossed electric field lines indicate? a field pointing in two directions
an attractive force on a charge
a nonuniform area of the field
a place where the field strength is zero

A14 kg rock starting from rest free falls through a distance of 5.0 m with no air resistance. find the momentum change of the rock caused by its fall and the resulting change in the magnitude of earths velocity. earth mass is 6.0 * 10^24 kg. show your work assuming the rock earth system is closed.