"""Tests for rotational dynamics calculations."""
from chuk_mcp_physics.rotational import (
TorqueRequest,
MomentOfInertiaRequest,
AngularMomentumRequest,
RotationalKineticEnergyRequest,
AngularAccelerationRequest,
calculate_torque,
calculate_moment_of_inertia,
calculate_angular_momentum,
calculate_rotational_kinetic_energy,
calculate_angular_acceleration,
)
class TestTorque:
def test_perpendicular_force(self):
"""Test torque with force perpendicular to position."""
request = TorqueRequest(
force=[50.0, 0.0, 0.0],
position=[0.0, 0.0, 0.8],
)
result = calculate_torque(request)
# τ = r × F, should be 40 N⋅m in y-direction
assert abs(result.torque[1] - 40.0) < 0.01
assert abs(result.magnitude - 40.0) < 0.01
def test_parallel_force_zero_torque(self):
"""Test that parallel force produces zero torque."""
request = TorqueRequest(
force=[10.0, 0.0, 0.0],
position=[1.0, 0.0, 0.0],
)
result = calculate_torque(request)
assert result.magnitude < 0.01
class TestMomentOfInertia:
def test_solid_sphere(self):
"""Test moment of inertia for solid sphere."""
request = MomentOfInertiaRequest(
shape="solid_sphere",
mass=5.0,
radius=0.3,
)
result = calculate_moment_of_inertia(request)
# I = (2/5) * m * r²
expected = (2.0 / 5.0) * 5.0 * 0.3 * 0.3
assert abs(result.moment_of_inertia - expected) < 0.001
def test_disk(self):
"""Test moment of inertia for disk."""
request = MomentOfInertiaRequest(
shape="disk",
mass=5.0,
radius=0.3,
)
result = calculate_moment_of_inertia(request)
# I = (1/2) * m * r²
expected = 0.5 * 5.0 * 0.3 * 0.3
assert abs(result.moment_of_inertia - expected) < 0.001
def test_rod_center(self):
"""Test moment of inertia for rod about center."""
request = MomentOfInertiaRequest(
shape="rod",
mass=2.0,
length=1.0,
axis="center",
)
result = calculate_moment_of_inertia(request)
# I = (1/12) * m * L²
expected = (1.0 / 12.0) * 2.0 * 1.0 * 1.0
assert abs(result.moment_of_inertia - expected) < 0.001
def test_rod_end(self):
"""Test moment of inertia for rod about end."""
request = MomentOfInertiaRequest(
shape="rod",
mass=2.0,
length=1.0,
axis="end",
)
result = calculate_moment_of_inertia(request)
# I = (1/3) * m * L²
expected = (1.0 / 3.0) * 2.0 * 1.0 * 1.0
assert abs(result.moment_of_inertia - expected) < 0.001
def test_box_x_axis(self):
"""Test moment of inertia for box about x-axis."""
request = MomentOfInertiaRequest(
shape="box",
mass=10.0,
width=2.0,
height=3.0,
depth=4.0,
axis="x",
)
result = calculate_moment_of_inertia(request)
# I = (1/12) * m * (h² + d²)
expected = (1.0 / 12.0) * 10.0 * (3.0 * 3.0 + 4.0 * 4.0)
assert abs(result.moment_of_inertia - expected) < 0.001
def test_box_y_axis(self):
"""Test moment of inertia for box about y-axis."""
request = MomentOfInertiaRequest(
shape="box",
mass=10.0,
width=2.0,
height=3.0,
depth=4.0,
axis="y",
)
result = calculate_moment_of_inertia(request)
# I = (1/12) * m * (w² + d²)
expected = (1.0 / 12.0) * 10.0 * (2.0 * 2.0 + 4.0 * 4.0)
assert abs(result.moment_of_inertia - expected) < 0.001
def test_box_z_axis(self):
"""Test moment of inertia for box about z-axis."""
request = MomentOfInertiaRequest(
shape="box",
mass=10.0,
width=2.0,
height=3.0,
depth=4.0,
axis="z",
)
result = calculate_moment_of_inertia(request)
# I = (1/12) * m * (w² + h²)
expected = (1.0 / 12.0) * 10.0 * (2.0 * 2.0 + 3.0 * 3.0)
assert abs(result.moment_of_inertia - expected) < 0.001
def test_hollow_sphere(self):
"""Test moment of inertia for hollow sphere."""
request = MomentOfInertiaRequest(
shape="hollow_sphere",
mass=5.0,
radius=0.3,
)
result = calculate_moment_of_inertia(request)
# I = (2/3) * m * r²
expected = (2.0 / 3.0) * 5.0 * 0.3 * 0.3
assert abs(result.moment_of_inertia - expected) < 0.001
class TestAngularMomentum:
def test_simple_angular_momentum(self):
"""Test angular momentum calculation."""
request = AngularMomentumRequest(
moment_of_inertia=3.0,
angular_velocity=[0.0, 5.0, 0.0],
)
result = calculate_angular_momentum(request)
# L = I * ω
assert abs(result.angular_momentum[1] - 15.0) < 0.01
assert abs(result.magnitude - 15.0) < 0.01
class TestRotationalKineticEnergy:
def test_rotational_ke(self):
"""Test rotational kinetic energy."""
request = RotationalKineticEnergyRequest(
moment_of_inertia=0.5,
angular_velocity=100.0,
)
result = calculate_rotational_kinetic_energy(request)
# KE = (1/2) * I * ω²
expected = 0.5 * 0.5 * 100.0 * 100.0
assert abs(result.rotational_ke - expected) < 0.1
class TestAngularAcceleration:
def test_angular_acceleration(self):
"""Test angular acceleration."""
request = AngularAccelerationRequest(
torque=10.0,
moment_of_inertia=0.5,
)
result = calculate_angular_acceleration(request)
# α = τ / I
expected = 10.0 / 0.5
assert abs(result.angular_acceleration - expected) < 0.01
