※ 绘制炸d轨迹 V——绘制多条轨迹

########## Begin ##########
import numpy as np
import matplotlib.pyplot as plt
def calBombTrace(h, v0):
    g,n = 9.8,30
    tmax = (2*h/g)**0.5
    t = np.linspace(0, tmax, n)
    xt = v0*t
    yt = h-1/2*g*t**2
    return xt, yt
H = [3000, 2000, 1000]
V0 = [200, 260, 230]
for h in H:
    for v0 in V0:
        xt,yt = calBombTrace(h,v0)
        plt.plot(xt,yt,'r-')
plt.grid('on')
plt.axis([0, 6500, 0, 3000])
plt.show()

########## End ##########
plt.savefig( 'src/step6/student/pic.png' )
plt.close()