A spring has a a constant of 650 N/m. How far must it be compressed to push a 4kg object on a friction-less surface to 3 m/s?
Let X be the required compression and V be the required velocity.
(Spring potential energy) = (Final kinetic energy of the mass)
(1/2) k X^2 = (1/2) M V^2
X = V*sqrt(M/k)= 0.235 m