Stroboscope photography is a commonly used experimental method to study variable speed motion. In a darkroom, the camera shutter is in a normally open state, and the strobe only emits a flash at regu

Stroboscope photography is a commonly used experimental method to study variable speed motion. In a darkroom, the camera shutter is in a normally open state, and the strobe only emits a flash at regular intervals.

(1) The ball performs a horizontal tossing motion. The horizontal tossing motion makes a uniform linear motion in the horizontal direction. Camera A captures the motion in the horizontal direction, so it should be points with equal distances. Therefore, the stroboscopic photo taken by camera A is picture b.

(2) Camera A captures the uniform linear motion of the ball in the horizontal direction, and camera B captures the free fall motion of the ball in the vertical direction. According to the measurement in Figure B (a), the OP distance is h=45cm ,

Then h=12gt2,

The solution is: t=2hg=2×0.4510=0.3s

The OP distance in (b) is s= 30cm, then s=v0t,

The initial velocity of the flat parabolic object is v0=st=0.30.3=1m/s.

The vertical velocity of point P is vy=gt=10×0.3m/s=3m/s,

So the velocity of point P is v= according to the Pythagorean theorem. v02+vy2＝33+12＝10m/s．

So the answer is: (1) b; (2) 1; 10.