An isolated system consists of two charged. particles of equal mass. Initially the particles are far apart, have zero potential energy, and one of the particles has nonzero speed. If the dissipation is neglected, which of the following is true for the total energy of the system at any later time?

• A

  It is negative and constant

• B

  It is positive and constant.

• C

  It is constant, but the sign cannot be determined unless the initial velocities of both particles are known.

• D

  It cannot be constant because the particles exert force on each other.