Let t be the time for people to walk 1km, then t= 1/v, and establish a spatial coordinate system with people as reference, then people will stand still in this coordinate system, and the rainfall rate will be (x-v, y, z) t. In the vertical direction, that is, the Z direction, the rainfall accepted by human body will be ZT * s/kloc-0. S2 is the front lateral area of human body, that is, the volume of rainwater received by human body in X direction is (x-v)t*S3, and S3 is the front lateral area of human body. The total amount of rainwater received is: (x-v) ts3+yts2+zts1= (x/v-1) S3+(y/v) S2. Observing this result, we can see that as long as we walk fast, we will get less rain.

If you want to substitute the numerical value to calculate the specific rainfall, you should pay attention to one thing. Under the rectangular model, people can only be caught in the rain in front or behind, and for the side, only one side can be caught in the rain and copied to death.