A particle is moving in a circular path of radius a under the action of an attractive potential $U = - \frac{k}{2r^2}$. Its total energy is :

Question

( A ) $- \frac{k}{4a^2}$
( B ) $- \frac{k}{2a^2}$
( C ) $-\frac{3}{2} \frac{k}{a^2}$
( D ) zero