② The trolley speed is V = (4.00+4.00) × 0.012× 0.02m/s = 2m/s..
③ According to the knowledge of mathematical function, the graph line may be a parabola (quadratic function) or a cubic function, but it cannot be a hyperbola or a square root curve, so the error CD of AB is correct, so the guess is definitely incorrect.
(2) (1) Because the current flowing through the small bulb is required to be adjusted from zero, the sliding rheostat should be connected in partial pressure. Because the internal resistance of ammeter can be ignored, ammeter should be connected internally. The circuit diagram is shown in the figure, and the physical connection diagram is shown in the figure below.
② As can be seen from the I-U diagram, when I=0.4A and U=6.0V, the power of the small bulb is P=UI=6.0×0.4W=2.4W?
So the answers are (1) 1cd, 22, 3ab.
? (2)① As shown in the figure, ②6.0, ② 2.4.