Photography table tennis

① The diameter of table tennis is 40mm, the diameter of table tennis in the photo is 12mm, and the falling distance of table tennis in the photo is 15mm.

In practice, the falling distance of table tennis is: s = 40mm12mm×15mm = 50mm = 0.05m.

∫S = 12gt 2，g= 10m/s2，

∴t2=2sg=2×0.05m 10m/s2=0.0 1s2，

Then the landing time of table tennis is: t=0. 1s,

The speed of table tennis is: v = ST = 0.05m0.1s = 0.5m/s.

(2) stroboscopic photography is shooting objects at the same time interval, so the distance traveled by the ball at the same time is recorded in the picture. The shorter the shutter exposure time, the clearer the recorded image.

So the answer is: 0.5; Short.