a1xt1=v1
a1x2=2;推出a1=1(m/s)²
v2-a3xt3=0
2-a3x3=0;推出a3=2/3(m/s²)
H=h1+h2+h3=1/2xa1(t1)²+h2+v2xt3-1/2xa3(t3)²=1/2x1x2²+15+2x3-1/2x2/3x3²=18(m)
a1xt1=v1
a1x2=2;推出a1=1(m/s)²
v2-a3xt3=0
2-a3x3=0;推出a3=2/3(m/s²)
H=h1+h2+h3=1/2xa1(t1)²+h2+v2xt3-1/2xa3(t3)²=1/2x1x2²+15+2x3-1/2x2/3x3²=18(m)