jupytersketcher/examples/pendulum1.py

from pysketcher import *

H = 7.
W = 6.

drawing_tool.set_coordinate_system(xmin=0, xmax=W,
                                   ymin=0, ymax=H,
                                   axis=False)
#drawing_tool.set_grid(True)
drawing_tool.set_linecolor('blue')

L = 5*H/7          # length
P = (W/6, 0.85*H)  # rotation point
a = 40             # angle

vertical = Line(P, P-point(0,L))
path = Arc(P, L, -90, a)
angle = Arc_wText(r'$\theta$', P, L/4, -90, a, text_spacing=1/30.)

rod = Line(P, P + L*point(sin(radians(a)), -L*cos(radians(a))))
# or shorter (and more reliable)
mass_pt = path.geometric_features()['end']
rod = Line(P, mass_pt)

mass = Circle(center=mass_pt, radius=L/20.)
mass.set_filled_curves(color='blue')
rod_vec = rod.geometric_features()['end'] - \
          rod.geometric_features()['start']
unit_rod_vec = unit_vec(rod_vec)
mass_symbol = Text('$m$', mass_pt + L/10*unit_rod_vec)

length = Distance_wText(P, mass_pt, '$L$')
# Displace length indication
length.translate(L/15*point(cos(radians(a)), sin(radians(a))))
gravity = Gravity(start=P+point(0.8*L,0), length=L/3)

def set_dashed_thin_blackline(*objects):
    """Set linestyle of objects to dashed, black, width=1."""
    for obj in objects:
        obj.set_linestyle('dashed')
        obj.set_linecolor('black')
        obj.set_linewidth(1)

set_dashed_thin_blackline(vertical, path)

fig = Composition(
    {'body': mass, 'rod': rod,
     'vertical': vertical, 'theta': angle, 'path': path,
     'g': gravity, 'L': length, 'm': mass_symbol})

fig.draw()
drawing_tool.display()
drawing_tool.savefig('tmp_pendulum1')

# Draw body diagram in several different versions
# (note that we build body_diagram, erase and draw,
# add elements to body_diagram, erase and draw, and so on)
input('Press Return to make body diagram: ')

drawing_tool.erase()

drawing_tool.set_linecolor('black')

rod_start = rod.geometric_features()['start']  # Point P
vertical2 = Line(rod_start, rod_start + point(0,-L/3))
set_dashed_thin_blackline(vertical2)
set_dashed_thin_blackline(rod)
angle2 = Arc_wText(r'$\theta$', rod_start, L/6, -90, a,
                   text_spacing=1/30.)

mg_force  = Force(mass_pt, mass_pt + L/5*point(0,-1),
                  '$mg$', text_pos='end')
rod_force = Force(mass_pt, mass_pt - L/3*unit_vec(rod_vec),
                  '$S$', text_pos='end',
                  text_spacing=(0.03, 0.01))
air_force = Force(mass_pt, mass_pt -
                  L/6*unit_vec((rod_vec[1], -rod_vec[0])),
                  '$\sim|v|v$', text_pos='end',
                  text_spacing=(0.04,0.005))

body_diagram = Composition(
    {'mg': mg_force, 'S': rod_force, 'rod': rod,
     'vertical': vertical2, 'theta': angle2,
     'body': mass, 'm': mass_symbol})

body_diagram.draw()
#drawing_tool.display('Body diagram')
drawing_tool.savefig('tmp_pendulum2')

drawing_tool.adjust_coordinate_system(body_diagram.minmax_coordinates(), 90)
#drawing_tool.display('Body diagram')
drawing_tool.savefig('tmp_pendulum3')

drawing_tool.erase()
body_diagram['air'] = air_force
body_diagram.draw()
#drawing_tool.display('Body diagram')
drawing_tool.savefig('tmp_pendulum4')

drawing_tool.erase()
x0y0 = Text('$(x_0,y_0)$', P + point(-0.4,-0.1))
ir = Force(P, P + L/10*unit_vec(rod_vec),
           r'$\boldsymbol{i}_r$', text_pos='end',
           text_spacing=(0.015,0))
ith = Force(P, P + L/10*unit_vec((-rod_vec[1], rod_vec[0])),
           r'$\boldsymbol{i}_{\theta}$', text_pos='end',
            text_spacing=(0.02,0.005))

body_diagram['ir'] = ir
body_diagram['ith'] = ith
body_diagram['origin'] = x0y0

body_diagram.draw()
#drawing_tool.display('Body diagram')
drawing_tool.savefig('tmp_pendulum5')

input()