Final answer:
The proton moves into a region of lower potential.
Step-by-step explanation:
The proton moves into a region of lower potential.
When a proton moves into an electric field, it experiences an electric force due to the interaction between its positive charge and the electric field. This force opposes the motion of the proton and acts in the direction opposite to its initial velocity. As a result, the proton's kinetic energy decreases, eventually bringing it to rest.
The work done by the electric field on the proton is negative, indicating a decrease in its potential energy. Since potential energy is directly related to electric potential, the movement of the proton from a region of higher potential energy (higher initial speed) to a region of lower potential energy (rest) implies that it moved into a region of lower potential.