When someone was taking pictures indoors with the window as the background, he happened to take a small stone falling from a height outside the window.

From the title ("The actual length of the window frame in the photo is 100cm, the length is 4.0cm"), it can be known that the ratio of the object to the scene in the photo is 25: 1.

Then the actual trajectory of the stone is: s solid =1.6 * 25 = 40 cm = 0.4 m.

According to the uniform motion formula S=V*t, the value of the substituted data is 0.4=V*0.02.

Solution: V = 20m m/s

And because according to the speed formula of acceleration, V=gt (not specified in the initial speed topic, it defaults to 0), so it is 20= 10t'

Solution, get: t'=2s.

Then substitute the data according to the formula of free fall H = 1/2gt 2: H = 1/2 * 10 * 2 2.

Solution: h=20m.

As for how high the stone fell, the title did not give how high it was from the ground when the photo was taken. I can't calculate it, but I know that the stone has fallen by 20 meters when I took the picture.