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I'm a little stuck on a problem involving voltage and conservation of energy. The answer that I came up with involved a negative value for kinetic energy, which doesn't make sense to me because mass and v^2 are never negative.

Problem: A proton is accelerated from rest by a uniform electric field. The proton experiences a potential decrease of 100 V. Find its final kinetic energy.

What I've done so far:

KE_i = 0 because accelerated from rest

V_b - V_a = -100 V

Change in voltage = Work/charge = [-q(int)E dot ds] / q = Change in potential energy

-100 = -Change in PE --> 100 J = change in potential energy

Therefore, under law of conservation of energy... change in kinetic energy must equal -100 J. Since KE_i = 0 J, KE_f= -100 J.

Thanks in advance for the help.