Solenoid Kinetic Energy
The datasheet for the solenoid is showing the attracting force for a mass attached to the plunger when the solenoid is oriented in the vertical direction and the mass hangs from the plunger. This is simply showing the maximum mass for which the solenoid can minimally counter the acceleration of gravity. 

Given the shape of the graph, it suggests that at the specified mass there is zero movement of the plunger from its plotted position. It follows then that the acceleration and velocity of the plunger, and therefore the mass, is likely zero throughout the plot.