t1=v/a1
t2=v/a2 得a1/a2=t1/t2 C正确
s1=1/2a1t1^2=0.5v^2/a1
s2=vt2-1/2a2t2^2=0.5V^2/a2
所以s1=0.5v*t1
s2=0.5*t2
A正确