Help! Self-study encountered a problem that I couldn't understand.

I have done this problem, and I can help you.

The number cloth on the chest is shaking at the moment of taking pictures, so the width of the blurred part is actually the displacement at the moment of taking pictures. How long does it take to take a picture in one second? That is, the exposure time of the camera is 1/60s, so as long as the width and time of the blurred part are known, the "photographing speed" of the numbered cloth at the moment of punching can be calculated. It is called "photographing speed" because it needs to be converted from the actual speed, and this conversion can be solved by H and H, so we can know the punching speed from the above data. You got it? Ask me if you don't understand.

And the displacement of d, 1 10 meter race, of course, 1 10. You must understand this.