def test10(self):
particles = Particles(2)
particles.position = [[1, 0, 0], [2,0,0]] | units.m
particles.velocity = [[3, 0, 0], [4,0,0]] | units.m / units.s
particles.mass = 1 | units.kg
self.assertEquals(particles.total_mass(), 2 | units.kg)
self.assertEquals(particles.total_momentum(), [7, 0, 0] | units.kg * units.m / units.s)
self.assertEquals(particles.total_momentum(), particles.total_mass() * particles.center_of_mass_velocity())
self.assertEquals(particles.total_radius(), 0.5 | units.m)
convert_nbody = nbody_system.nbody_to_si(1000 | units.kg, 1e-6 | units.m)
numpy.random.seed(123)
field = new_plummer_sphere(10000, convert_nbody) # small clump of particles, can be regarded as point mass
self.assertAlmostRelativeEquals(particles.potential_energy_in_field(field), -constants.G * (1500 | units.kg**2 / units.m), 5)
self.assertAlmostEquals(particles.potential_energy_in_field(field), -1.001142 | 1e-7 * units.kg * units.m**2 / units.s**2, 5)
field.position *= ((5 | units.m) / field.position.lengths()).reshape((-1, 1)) # spherical shell around particles
potential_energy = particles.potential_energy_in_field(field)
particles.position += [0, 1, 2] | units.m # as long as particles remain inside the shell, the potential doesn't change
self.assertAlmostEquals(particles.potential_energy_in_field(field), potential_energy, 5)
particles.mass = [1, 2] | units.kg
self.assertAlmostRelativeEquals(particles.potential(), -constants.G * ([2, 1] | units.kg / units.m))
self.assertAlmostRelativeEquals(particles.potential()[0], particles[0].potential())
self.assertAlmostRelativeEquals(particles.potential()[1], particles[1].potential())
def test10(self):
particles = Particles(2)
particles.position = [[1, 0, 0], [2, 0, 0]] | units.m
particles.velocity = [[3, 0, 0], [4, 0, 0]] | units.m / units.s
particles.mass = 1 | units.kg
self.assertEquals(particles.total_mass(), 2 | units.kg)
self.assertEquals(particles.total_momentum(),
[7, 0, 0] | units.kg * units.m / units.s)
self.assertEquals(
particles.total_momentum(),
particles.total_mass() * particles.center_of_mass_velocity())
self.assertEquals(particles.total_radius(), 0.5 | units.m)
convert_nbody = nbody_system.nbody_to_si(1000 | units.kg,
1e-6 | units.m)
numpy.random.seed(123)
field = new_plummer_sphere(
10000, convert_nbody
) # small clump of particles, can be regarded as point mass
self.assertAlmostRelativeEquals(
particles.potential_energy_in_field(field),
-constants.G * (1500 | units.kg**2 / units.m), 5)
self.assertAlmostEquals(
particles.potential_energy_in_field(field),
-1.001142 | 1e-7 * units.kg * units.m**2 / units.s**2, 5)
field.position *= ((5 | units.m) / field.position.lengths()).reshape(
(-1, 1)) # spherical shell around particles
potential_energy = particles.potential_energy_in_field(field)
particles.position += [
0, 1, 2
] | units.m # as long as particles remain inside the shell, the potential doesn't change
self.assertAlmostEquals(particles.potential_energy_in_field(field),
potential_energy, 5)
particles.mass = [1, 2] | units.kg
self.assertAlmostRelativeEquals(
particles.potential(),
-constants.G * ([2, 1] | units.kg / units.m))
self.assertAlmostRelativeEquals(particles.potential()[0],
particles[0].potential())
self.assertAlmostRelativeEquals(particles.potential()[1],
particles[1].potential())
