S=10000
t1=120
t3=60
v0=15
S=S1+S2+S3
S1=a1*t1^2/2
S2=v2*t2
S3=a3*t3^2/2
t1+t2+t3=t
v0=S/t
v2=a1*t1
v2=a2*t2
v2-?
*******************
S=a1*t1^2/2+v2*t2+a3*t3^2/2
S= v0*(t1+t2+t3)
a1=v2/t1
a3=v2/t3
v2-?
*******************
S=(v2/t1)*t1^2/2+v2*t2+(v2/t3)*t3^2/2
t2=(S/v0)-(t1+t3)
v2-?
*******************
S=v2*t1/2+v2*(S/v0-t1-t3)+v2*t3/2
v2-?
*******************
v2=S/(t1/2+S/v0-t1-t3+t3/2) = 10000/(120/2+10000/15-120-60+60/2) =
17,34104 м/c