text: we can use work energy theorem.i.e. work done by all the forces(force of gravity= -0.3*9.8(.05m) +work done by spring force =1/2 k(Xf^2-Xi^2)  )is equql to change in kinetic energy i.e.1/2mV^2-1/2mu^2.  where u=0 .i think u should try this.thanks