A particle of mass M rests on a straight groove along which it is constrained to move. A perfectly elastic rubber band of natural length l and uniform area of cross-section is attached with the particle. The other end of the band is suspended from a rigid support. A force K(l '2 - l 2 ) 1/2 is required to stretch the band to a length l'. The particle is moved to a distance S (where S << 1) and then released. Taking K = and μ μ as the coefficient of friction between the particle and the groove, the velocity of particle when passing through the initial position is