1. Average speed = (initial speed+final speed) ÷2

2. Rolling time = distance traveled/average speed

3. Speed * * * Decrease = Maximum Speed-Minimum Speed

4. Average speed decrease per second = * * * decrease ÷ scrolling time

The third question is more difficult. Remember, it takes x seconds. First, find the instantaneous speed of 5 meters, which is the difference between the initial speed of 5 minus x seconds and the average deceleration per second. Then, the average speed of this section from the beginning to 5 meters is equal to the sum of the speed at the beginning of 5 plus the instantaneous speed of 5 meters divided by 2. The average speed of this section multiplied by time x equals distance 5. Just solve this unary quadratic equation.

I only gave you the method, which is a general method. All kinds of problems can be done according to this step.