1、
先求小球下落的时间
t=(2H/g)^(0.5)=(2*100m/10m/s^2)^(0.5)=4.47s
n=int(t/Δt)=4.47s/0.5s=8 (注：int是取整函数）
当最下面的球落地前瞬间,最上面的小球下落0.47s,所以
h=gt^2/2=10m/s^2*(0.47s)^2/2=1.1m
ΔH=H-h=100m-1.1m=98.9m
2、54km/h=15m/s
t1=v/a1=15m/s/0.5m/s^2=30s
x1=v^2/2a1=(15m/s)^2/(2*0.5m/s^2)=225m
t1'=x1/v=225m/15m/s=15s
t2=2min=120s
t3=v/a2=15m/s/0.3m/s^2=50s
x2=v^2/2a2=(15m/s)^2/(2*0.3m/s^2)=375m
t3'=x2/v=375m/15m/s=25s
T=(t1-t1')+t2+(t3-t3')=(30s-15s)+120s+(50s-25s)=160s
3、
H=gt^2/2
H-9H/25=g(t-1)^2/2
解方程组得：t=5s H=125m