Rotation and Elongation of a spring - 2

A very long thin tube is hinged at a point such that its free to rotate in the horizontal plane.Inside the tube there is spring fixed at its end.the spring is connected to a mass $m$ which precisely fits into the tube. At the instant $t=0$ when the spring is in its natural length $R$ ; the mass is given velocity $V$ in a direction perpendicular to the length of the tube.

As the spring elongates the mass also acquires a velocity along the length of the tube

If the deformation in the spring at the instant when 'Vt' (velocity of the mass along the length of the tube) has reached its max. value is 'X' then find 100X*((1+X)^3)

FOR m=2Kg V=1m/s k=200N/m R=1m