The potential energy of a particle in a force field is U=Ar2−Br where A and B are positive constants and r is the distance of particle from the centre of the field For stable equilibrium the distance of the particle is
1)A/B
2)B/A
3)B/2A
4)2A/B
Potential energy is given as; U=Ar2−Br
For condition of stable equilibrium force should be zero or change in potentia energy will be zero.
F=−dUdr=0
F=dAr2dr−dBrdr
0=−2Ar−3−(−Br−2)
−2Ar−3=(−Br−2)
2AB=r
So, For condition of stable equilibrium diustance should be,
2AB=r