t∈{7;8} s
d1=at1²/2=7²a/2=24,5a
d2=at2²/2=8²a/2=32a
d=d2-d1=7,5a
30=7,5a=>a=30/7,5=4 m/s²
t1∈{0,1)
d1'=at1'²/2=0²*4/2=0
d2'=at2²/2=1²*4/2=2
d'=d2'-d1'=2-0=2 m
