A train moves uniformly in a straight line with an initial speed of 2m / s and an acceleration of 0.5m/s2. The speed of the train at the end of the third second is______ M / s, the average velocity in the first four seconds is______ M / s, the displacement in the fifth second is______ m．

A train moves uniformly in a straight line with an initial speed of 2m / s and an acceleration of 0.5m/s2. The speed of the train at the end of the third second is______ M / s, the average velocity in the first four seconds is______ M / s, the displacement in the fifth second is______ m．

(1) According to the speed time formula, v = V0 + at = 2 + 0.5 × 3m / S = 3.5m/s. (2) the average speed of the train is obtained when the displacement x = v0t + 12at2 = 2 × 4 + 12 × 0.5 × 42m = 12m in the first four seconds. V = XT = 124m / S = 3m / S. (3) the displacement x ′ = X5 − X4 = v0t ′ + 12At ′ 2 − x = 4.25m in the fifth second, so the answer is: 3.5 & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; & nbsp; 4.25