64 lines
2.1 KiB
Python
64 lines
2.1 KiB
Python
|
from sympy.core.symbol import symbols
|
||
|
|
from sympy.physics.mechanics import Point, Particle, ReferenceFrame, inertia
|
||
|
|
|
||
|
|
from sympy.testing.pytest import raises, warns_deprecated_sympy
|
||
|
|
|
||
|
|
|
||
|
|
def test_particle():
|
||
|
|
m, m2, v1, v2, v3, r, g, h = symbols('m m2 v1 v2 v3 r g h')
|
||
|
|
P = Point('P')
|
||
|
|
P2 = Point('P2')
|
||
|
|
p = Particle('pa', P, m)
|
||
|
|
assert p.__str__() == 'pa'
|
||
|
|
assert p.mass == m
|
||
|
|
assert p.point == P
|
||
|
|
# Test the mass setter
|
||
|
|
p.mass = m2
|
||
|
|
assert p.mass == m2
|
||
|
|
# Test the point setter
|
||
|
|
p.point = P2
|
||
|
|
assert p.point == P2
|
||
|
|
# Test the linear momentum function
|
||
|
|
N = ReferenceFrame('N')
|
||
|
|
O = Point('O')
|
||
|
|
P2.set_pos(O, r * N.y)
|
||
|
|
P2.set_vel(N, v1 * N.x)
|
||
|
|
raises(TypeError, lambda: Particle(P, P, m))
|
||
|
|
raises(TypeError, lambda: Particle('pa', m, m))
|
||
|
|
assert p.linear_momentum(N) == m2 * v1 * N.x
|
||
|
|
assert p.angular_momentum(O, N) == -m2 * r *v1 * N.z
|
||
|
|
P2.set_vel(N, v2 * N.y)
|
||
|
|
assert p.linear_momentum(N) == m2 * v2 * N.y
|
||
|
|
assert p.angular_momentum(O, N) == 0
|
||
|
|
P2.set_vel(N, v3 * N.z)
|
||
|
|
assert p.linear_momentum(N) == m2 * v3 * N.z
|
||
|
|
assert p.angular_momentum(O, N) == m2 * r * v3 * N.x
|
||
|
|
P2.set_vel(N, v1 * N.x + v2 * N.y + v3 * N.z)
|
||
|
|
assert p.linear_momentum(N) == m2 * (v1 * N.x + v2 * N.y + v3 * N.z)
|
||
|
|
assert p.angular_momentum(O, N) == m2 * r * (v3 * N.x - v1 * N.z)
|
||
|
|
p.potential_energy = m * g * h
|
||
|
|
assert p.potential_energy == m * g * h
|
||
|
|
# TODO make the result not be system-dependent
|
||
|
|
assert p.kinetic_energy(
|
||
|
|
N) in [m2*(v1**2 + v2**2 + v3**2)/2,
|
||
|
|
m2 * v1**2 / 2 + m2 * v2**2 / 2 + m2 * v3**2 / 2]
|
||
|
|
|
||
|
|
|
||
|
|
def test_parallel_axis():
|
||
|
|
N = ReferenceFrame('N')
|
||
|
|
m, a, b = symbols('m, a, b')
|
||
|
|
o = Point('o')
|
||
|
|
p = o.locatenew('p', a * N.x + b * N.y)
|
||
|
|
P = Particle('P', o, m)
|
||
|
|
Ip = P.parallel_axis(p, N)
|
||
|
|
Ip_expected = inertia(N, m * b**2, m * a**2, m * (a**2 + b**2),
|
||
|
|
ixy=-m * a * b)
|
||
|
|
assert Ip == Ip_expected
|
||
|
|
|
||
|
|
def test_deprecated_set_potential_energy():
|
||
|
|
m, g, h = symbols('m g h')
|
||
|
|
P = Point('P')
|
||
|
|
p = Particle('pa', P, m)
|
||
|
|
with warns_deprecated_sympy():
|
||
|
|
p.set_potential_energy(m*g*h)
|