Answer:
57 eV
Explanation:
[tex]d[/tex] = separation between the plates = 4.9 mm = 0.0049 m
[tex]\Delta V[/tex] = Potential difference between the plates = 57 Volts
[tex]q[/tex] = magnitude of charge on proton = 1 e
[tex]K[/tex] = Kinetic energy of the proton
Using conservation of energy
Kinetic energy lost = Electric potential energy gained
[tex]K = q \Delta V\\K = (1 e) (57 )\\K = 57 eV[/tex]