An experimental group uses the experimental device shown in Figure A to verify whether the mechanical energy of the system composed of hook code and slider is conserved after static release. Before the experiment ( 1)0.48; 0.40; (2)②; (3)MGS； (4)①

The width of the narrow shutter measured by vernier caliper represents the displacement of the object, the digital timer records the time of passing through the photoelectric gate, the average speed of the object passing through the photoelectric gate is calculated by the displacement formula, the instantaneous speed v of the object is replaced by the average speed, and the height h of the hook code falling, that is, the distance s from the initial position of the shutter on the slider to the photoelectric gate. The law of conservation of mechanical energy can be verified by whether the mgs sum is equal.