13.
(1)由h1=1/2at1^2 a=2h1/t^2=5m/s^2
v1=at1=20m/s
(2)h2=v1^2/2g=400/20=20m
H=h1+h2=60m
(3) t2=v1/g=2s
H=1/2gt3^2 t3=(120/10)^1/2=3.5s
t=t1+t2+t3=9.5s
14.设水滴到窗台的时间t
L=1/2gt^2-1/2g(t-0.2)^2=1.4
t=0.8s
v=gt=8m/s
h=1/2gt^2=3.2m
13.
(1)由h1=1/2at1^2 a=2h1/t^2=5m/s^2
v1=at1=20m/s
(2)h2=v1^2/2g=400/20=20m
H=h1+h2=60m
(3) t2=v1/g=2s
H=1/2gt3^2 t3=(120/10)^1/2=3.5s
t=t1+t2+t3=9.5s
14.设水滴到窗台的时间t
L=1/2gt^2-1/2g(t-0.2)^2=1.4
t=0.8s
v=gt=8m/s
h=1/2gt^2=3.2m