刹住车需要 10÷4=2.5s所以3s的位移实际上是2.5s的位移,因为汽车已经停住了.刹车2s后,位移S = vt + 1/2 at^2 = 10x2 - 1/2 x 4 x 2^2 = 12m刹车3s后,位移S = vt + 1/2 at^2 = 10x2.5 - 1/2 x 4 x 2.5^2 = 12.5m 很高...