1. The problem statement, all variables and given/known data A particle moves in a circular orbit under the action of a force f(r)=-(k/r^2).If k is suddenly reduced to half its value, what would be the nature of the orbit? 2. Relevant equations e=sqrt[1+(2*L^2*E)/(mk^2)] 3. The attempt at a solution My attempt: Clearly,the particle moves under attractive central force.Now,for the circular orbit,eccentricity e=0 and as the motion is bound,the energy is negative. If k is reduced to k/2, eccentricity changes to e=1+(8*L^2*E)/(mk^2)=6*L^2*E/(mk^2) Since e becomes negative as E is negative,no motion is possible. Am I correct?