JEE Advanced 2020 Paper 1

One end of a spring of negligible unstretched length and spring constant k is fixed at the origin (0,0) . a point particle of mass m carrying a positive charge q is attached at its other end. The entiresystem is kept on a smooth horizontal surface. When a point dipole

→

p

pointing towards the chargeq is fixed at the origin, the spring gets stretched to a length I and attains a new equilibrium position (see figure below). If the point mass is now displaced slightly by Δl<<l from its equalibrium positionand released, it is found to oscillate at frequency

1

δ

√

k

m

. The value of δ is________.