Final answer:
The speed of the cylinder just after it moves away from the spring is determined at the point of zero compression, where the spring's potential energy has been fully converted into the cylinder's kinetic energy according to the principle of conservation of energy.
Step-by-step explanation:
To determine the speed of a cylinder just after it moves away from the spring, we should consider the point of zero compression in the spring. At this point, all the stored potential energy in the spring has been converted into kinetic energy of the cylinder. Using the conservation of energy principle, we can equate the potential energy stored in the spring at maximum compression to the kinetic energy of the cylinder at the point of release. The potential energy in the spring is given by PE = 1/2 kx^2 where k is the spring constant and x is the compression distance. The kinetic energy is given by KE = 1/2 mv^2 where m is the mass of the object and v is its velocity.