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 non-zero speed. If the radiation is neglected, which of the following is true for the total enrgy of the system at any later time ?

Options

A. It is negative and constant
B. It is positive and constant
C. It is constant, but the sign cannot be determind unless the initial velocities of both particles are known.
D. It cannot be constant of the motion because the particles exert force on each other.

Answer

B

Explanation

The initial potential energy of the isolated system zero and the initial kinetic energy of the system nonzero. No dissipative forces act within the system. Hence net energy of system is constant and equal initial kinetic energy of the system and hence positive.