a1=2.5m/s^2,t1=8s;a2=1.5m/s^2,t2=20s.
(1)从t=0到t1=8s:v1(=2.5t)>v2,无法追上;
从t1=8s到t2=20s:s1=a1*t1^2/2+20*(t-t1) s2=a2*t^2/2 由s1=s2解得:t=(40±2sqrt10)/3;
t>20s:s1=a1*t1^2/2+20*(t-t1) s2=a2*t2^2/2+30*(t-t2) t=22s;
(2)最大距离时两车速度相等,亦即v2=20m/s 故时间为10s Δs=45m
a1=2.5m/s^2,t1=8s;a2=1.5m/s^2,t2=20s.
(1)从t=0到t1=8s:v1(=2.5t)>v2,无法追上;
从t1=8s到t2=20s:s1=a1*t1^2/2+20*(t-t1) s2=a2*t^2/2 由s1=s2解得:t=(40±2sqrt10)/3;
t>20s:s1=a1*t1^2/2+20*(t-t1) s2=a2*t2^2/2+30*(t-t2) t=22s;
(2)最大距离时两车速度相等,亦即v2=20m/s 故时间为10s Δs=45m