TheAlgorithms/Python · error · ValueError

Gravitational force can not be negative

Error message

Gravitational force can not be negative

What it means

Raised by gravitational_law() when the force argument is negative. Newtonian gravitational force magnitude is physically non-negative, so a negative input force is rejected before the solver branches run. The check fires even when force is the known value, not the 0 placeholder.

Source

Thrown at physics/newtons_law_of_gravitation.py:75

    ValueError: One and only one argument must be 0

    >>> gravitational_law(force=36337.283, mass_1=-674, mass_2=0, distance=35584)
    Traceback (most recent call last):
        ...
    ValueError: Mass can not be negative

    >>> gravitational_law(force=-847938e12, mass_1=674, mass_2=0, distance=9374)
    Traceback (most recent call last):
        ...
    ValueError: Gravitational force can not be negative
    """

    product_of_mass = mass_1 * mass_2

    if (force, mass_1, mass_2, distance).count(0) != 1:
        raise ValueError("One and only one argument must be 0")
    if force < 0:
        raise ValueError("Gravitational force can not be negative")
    if distance < 0:
        raise ValueError("Distance can not be negative")
    if mass_1 < 0 or mass_2 < 0:
        raise ValueError("Mass can not be negative")
    if force == 0:
        force = GRAVITATIONAL_CONSTANT * product_of_mass / (distance**2)
        return {"force": force}
    elif mass_1 == 0:
        mass_1 = (force) * (distance**2) / (GRAVITATIONAL_CONSTANT * mass_2)
        return {"mass_1": mass_1}
    elif mass_2 == 0:
        mass_2 = (force) * (distance**2) / (GRAVITATIONAL_CONSTANT * mass_1)
        return {"mass_2": mass_2}
    elif distance == 0:
        distance = (GRAVITATIONAL_CONSTANT * product_of_mass / (force)) ** 0.5
        return {"distance": distance}
    raise ValueError("One and only one argument must be 0")

View on GitHub (pinned to f5988cc097)

Solutions

1. Pass the magnitude: force=abs(force) if the sign only encoded direction
2. If negative values indicate a repulsive/attractive convention upstream, convert to the magnitude before calling
3. Sanitize imported datasets with force = abs(force) or drop rows with force < 0

Example fix

# before
gravitational_law(force=-847938e12, mass_1=674, mass_2=0, distance=9374)
# ValueError: Gravitational force can not be negative

# after
gravitational_law(force=abs(-847938e12), mass_1=674, mass_2=0, distance=9374)

if force < 0:
    force = abs(force)  # only if sign encoded direction
# or reject:
assert force >= 0, "force must be a non-negative magnitude"

def is_non_negative(v) -> bool:
    return isinstance(v, (int, float)) and v >= 0

try:
    gravitational_law(force, m1, m2, d)
except ValueError as e:
    if "force can not be negative" in str(e).lower():
        gravitational_law(abs(force), m1, m2, d)
    else:
        raise

When it happens

Trigger: gravitational_law(force=-847938e12, mass_1=674, mass_2=0, distance=9374) — exactly one zero so the count check passes, but force < 0 raises immediately.

Common situations: Feeding signed vector components (attractive force coded as negative) into a magnitude-based API; parsing CSV data where a minus sign was a typo or a direction convention; reusing data from an orbital-mechanics library that signs its forces.

Related errors

• Distance can not be negative
• Mass can not be negative
• The length should be non-negative
• The mass of a body cannot be negative
• The height above the ground cannot be negative

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/756a934e2e2347ad. Report an issue: GitHub.