Stroboscopic photography is a commonly used experimental method to study the motion of objects. The camera is exposed regularly to record the position of the object.

(1) It takes 0.02s×3=0.06s for the ball to fall vertically from position A to position B,

Then the average speed of ball B is V = ST = 3m0.06s = 5m/s..

(2) Ball A moves the same distance in the same time, and A moves in a straight line, so A moves in a straight line at a constant speed; B travels different distances in the same time, and B moves in a straight line, so B moves in a variable speed straight line. Therefore, the ball A is in equilibrium.

(3) The ball A moves in a straight line at a uniform speed, and the vertical upward resistance of the ball A and the vertical downward gravity are a pair of equal balancing forces; When B moves in an accelerated straight line, its gravity is greater than its resistance.

A and B have the same gravity, so the resistance of A is greater than that of B. 。

So the answer is: (1) 5; (2) A; (3) greater than.