The cyclist moves in a straight line with uniform deceleration at an initial speed of 5 m / s, and the acceleration is 0.4 m / S2 (1) How long does it take to cross the distance of 30 meters? (2) What is the displacement in the second second? (3) What is the initial speed of the fifth second? (it can be solved by image)

1. According to the displacement formula: S = v0t + 1 / 2at ^ 2 into the data, we can get: T = 10 or T = 15s. From 0 = 5-0.4t, we can get that the deceleration time to zero is t = 12.5s, so t = 10s2, the displacement in the first second is S1 = 5-1 / 2 * 0.4 = 4.8m, the displacement in the first two seconds is S2 = 5 * 2-1 / 2 * 0.4 * 2 ^ 2 = 9.2m, so in the second

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