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- from pytest import raises
- from sympy import symbols
- from sympy.physics.mechanics import (RigidBody, Particle, ReferenceFrame, Point,
- outer, dynamicsymbols, Force, Torque)
- from sympy.physics.mechanics.loads import gravity, _parse_load
- def test_force_default():
- N = ReferenceFrame('N')
- Po = Point('Po')
- f1 = Force(Po, N.x)
- assert f1.point == Po
- assert f1.force == N.x
- assert f1.__repr__() == 'Force(point=Po, force=N.x)'
- # Test tuple behaviour
- assert isinstance(f1, tuple)
- assert f1[0] == Po
- assert f1[1] == N.x
- assert f1 == (Po, N.x)
- assert f1 != (N.x, Po)
- assert f1 != (Po, N.x + N.y)
- assert f1 != (Point('Co'), N.x)
- # Test body as input
- P = Particle('P', Po)
- f2 = Force(P, N.x)
- assert f1 == f2
- def test_torque_default():
- N = ReferenceFrame('N')
- f1 = Torque(N, N.x)
- assert f1.frame == N
- assert f1.torque == N.x
- assert f1.__repr__() == 'Torque(frame=N, torque=N.x)'
- # Test tuple behaviour
- assert isinstance(f1, tuple)
- assert f1[0] == N
- assert f1[1] == N.x
- assert f1 == (N, N.x)
- assert f1 != (N.x, N)
- assert f1 != (N, N.x + N.y)
- assert f1 != (ReferenceFrame('A'), N.x)
- # Test body as input
- rb = RigidBody('P', frame=N)
- f2 = Torque(rb, N.x)
- assert f1 == f2
- def test_gravity():
- N = ReferenceFrame('N')
- m, M, g = symbols('m M g')
- F1, F2 = dynamicsymbols('F1 F2')
- po = Point('po')
- pa = Particle('pa', po, m)
- A = ReferenceFrame('A')
- P = Point('P')
- I = outer(A.x, A.x)
- B = RigidBody('B', P, A, M, (I, P))
- forceList = [(po, F1), (P, F2)]
- forceList.extend(gravity(g * N.y, pa, B))
- l = [(po, F1), (P, F2), (po, g * m * N.y), (P, g * M * N.y)]
- for i in range(len(l)):
- for j in range(len(l[i])):
- assert forceList[i][j] == l[i][j]
- def test_parse_loads():
- N = ReferenceFrame('N')
- po = Point('po')
- assert _parse_load(Force(po, N.z)) == (po, N.z)
- assert _parse_load(Torque(N, N.x)) == (N, N.x)
- f1 = _parse_load((po, N.x)) # Test whether a force is recognized
- assert isinstance(f1, Force)
- assert f1 == Force(po, N.x)
- t1 = _parse_load((N, N.y)) # Test whether a torque is recognized
- assert isinstance(t1, Torque)
- assert t1 == Torque(N, N.y)
- # Bodies should be undetermined (even in case of a Particle)
- raises(ValueError, lambda: _parse_load((Particle('pa', po), N.x)))
- raises(ValueError, lambda: _parse_load((RigidBody('pa', po, N), N.x)))
- # Invalid tuple length
- raises(ValueError, lambda: _parse_load((po, N.x, po, N.x)))
- # Invalid type
- raises(TypeError, lambda: _parse_load([po, N.x]))
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