Question

汽车进站刹车时的初速度为18km/h,刹车速度为0.4m/s²,求经过10s时汽车的速度?15s内汽

Answer 1

简单呀；

18km/h=5m/s;

--> a=0,4

so V=V0+at;

t=10s;

then v=5-0.4*10;

V= 1m/s;

in 15s the car have been stopped at 5/0.4=12.5s,so last 2.5s the car is keeping static;

then all the distance the car travelled was:

1/2 × a × t^2 = 0.5* 0.4 * 12.5^2 = 31.25m;

or (0+5)/2 * 12.5 = 31.25m;

That's so easy,so keeping thinking by yourself;