Someone's photographic work.

The actual length of the 000cm window frame in the photo is 4 cm. So the actual length of the stone movement trajectory is:

△x=0.6×0004=40cm=0.4m

So the speed of the stone is approximately = △×△ t = 0.40.0m = m0m/s.

According to the person in free fall =gt, there is

T = person g = m000s = ms

So choose 0.