sitelen:Inclinedthrow.gif
Inclinedthrow.gif (400 × 288 pixels, file size: 374 KB, MIME type: image/gif en looped en 102 frames en 10 s)
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DescriptionInclinedthrow.gif |
English: Trajectories of three objects thrown at the same angle (70°). The black object doesn't experience any form of drag and moves along a parabola. The blue object experiences Stokes' drag, and the green object Newton drag. |
nanpa tenpo | |
Source | Own work |
jan sitelen | AllenMcC. |
Other versions | Inclinedthrow2.gif |
GIF genesis InfoField | This plot was created with Matplotlib. |
Source code InfoField | Python code#!/usr/bin/python3
# -*- coding: utf8 -*-
import os
import inspect
from math import *
import numpy as np
from scipy.integrate import odeint
from scipy.optimize import newton
import matplotlib as mpl
import matplotlib.pyplot as plt
from matplotlib import animation
# settings
mpl.rcParams['path.snap'] = False
fname = 'inclinedthrow'
size = 400, 288
l, w, b, h = 22.5/size[0], 1-23/size[0], 22.5/size[1], 1-23/size[1]
nframes = 102
delay = 8
lw = 1.
ms = 6
c1, c2, c3 = "#000000", "#0000ff", "#007100"
def projectile_motion(g, mu, pot, xy0, vxy0, tt):
# use a four-dimensional vector function vec = [x, y, vx, vy]
def dif(vec, t):
# time derivative of the whole vector vec
v = hypot(vec[2], vec[3])
vxrel, vyrel = vec[2] / v, vec[3] / v
return [vec[2], vec[3], -mu * v**pot * vxrel, -g - mu * v**pot * vyrel]
# solve the differential equation numerically
vec = odeint(dif, [xy0[0], xy0[1], vxy0[0], vxy0[1]], tt)
return vec[:, 0], vec[:, 1], vec[:, 2], vec[:, 3] # return x, y, vx, vy
g = 1.
theta = radians(70)
v0 = sqrt(g/sin(2*theta))
vinf = 2.1
# use identical terminal velocity vinf for both types of friction
mu_stokes = g / vinf**1
mu_newton = g / vinf**2
x0, y0 = 0.0, 0.0
vx0, vy0 = v0 * cos(theta), v0 * sin(theta)
T = newton(lambda t: projectile_motion(g, 0, 0, (x0, y0), (vx0, vy0), [0, t])[1][1], 2*vy0/g)
nsub = 10
tt = np.linspace(0, T * nframes / (nframes - 1), (nframes - 1) * nsub + 1)
traj_free = projectile_motion(g, 0, 0, (x0, y0), (vx0, vy0), tt)
traj_stokes = projectile_motion(g, mu_stokes, 1, (x0, y0), (vx0, vy0), tt)
traj_newton = projectile_motion(g, mu_newton, 2, (x0, y0), (vx0, vy0), tt)
def animate(nframe, saveframes=False):
print(nframe, '/', nframes)
t = T * float(nframe) / nframes
plt.clf()
fig.gca().set_position((l, b, w, h))
fig.gca().set_aspect("equal")
plt.xlim(0, 1)
plt.ylim(0, (h*size[1]) / (w*size[0]))
plt.xticks([]), plt.yticks([])
plt.xlabel('Distance', size=12)
plt.ylabel('Height', size=12)
plt.plot(traj_free[0][:nframe*nsub+1], traj_free[1][:nframe*nsub+1],
'-', lw=lw, color=c1)
plt.plot(traj_free[0][nframe*nsub], traj_free[1][nframe*nsub],
'ok', color=c1, markersize=ms, markeredgewidth=0)
plt.plot(traj_stokes[0][:nframe*nsub+1], traj_stokes[1][:nframe*nsub+1],
'-', lw=lw, color=c2)
plt.plot(traj_stokes[0][nframe*nsub], traj_stokes[1][nframe*nsub],
'ok', color=c2, markersize=ms, markeredgewidth=0)
plt.plot(traj_newton[0][:nframe*nsub+1], traj_newton[1][:nframe*nsub+1],
'-', lw=lw, color=c3)
plt.plot(traj_newton[0][nframe*nsub], traj_newton[1][nframe*nsub],
'ok', color=c3, markersize=ms, markeredgewidth=0)
if saveframes:
# export frame
dig = int(ceil(log10(nframes)))
fsavename = ('frame{:0' + str(dig) + '}.svg').format(nframe)
fig.savefig(fsavename)
with open(fsavename) as f: content = f.read()
content = content.replace('pt"', 'px"').replace('pt"', 'px"')
with open(fsavename, 'w') as f: f.write(content)
fig = plt.figure(figsize=(size[0]/72., size[1]/72.))
os.chdir(os.path.dirname(os.path.abspath(inspect.getfile(inspect.currentframe()))))
for i in range(nframes):
animate(i, True)
os.system('convert -loop 0 -delay ' + str(delay) + ' frame*.svg +dither ' + fname + '.gif')
# keep last frame for two seconds
os.system('gifsicle -k32 --color-method blend-diversity -b ' + fname + '.gif -d' + str(delay) + ' "#0-' + str(nframes-2) + '" -d200 "#' + str(nframes-1) + '"')
for i in os.listdir('.'):
if i.startswith('frame') and i.endswith('.svg'):
os.remove(i)
|
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tenpo | sitelen lili | suli | jan | o toki | |
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current | 2020-10-21T16:10:04 | 400 × 288 (374 KB) | wikimediacommons>Geek3 | adjusted friction coefficients such to make terminal velocity of both trajectories equal. In this case, the Newton projectile moves further. |
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