The average speed of the car in the fifth second can be calculated by making the car move in a straight line with the acceleration of 2m / S2 from the static state______ ．

The average speed of the car in the fifth second can be calculated by making the car move in a straight line with the acceleration of 2m / S2 from the static state______ ．

The acceleration of the car is 2m / S2. If the displacement of the car in the fifth second is x, then the displacement in the first five seconds is X5 = 12at52, the displacement in the first four seconds is X4 = 12at42, & nbsp; then there is x5-x4 = x, and the average velocity in the fifth second is. V = XT. Substituting the data, we get. V = 91m / S = 9m / s, so the answer is: 9