TheAlgorithms/Python · error · ValueError

The height above the ground cannot be negative

Error message

The height above the ground cannot be negative

What it means

Raised by potential_energy(mass, height) in physics/potential_energy.py when height < 0. Height is measured above the ground reference, so negative heights are rejected; height 0 with any non-negative mass returns 0.0. The mass check runs first, so a negative mass masks a negative height error.

Source

Thrown at physics/potential_energy.py:54

    >>> potential_energy(0,5)
    0.0
    >>> potential_energy(8,0)
    0.0
    >>> potential_energy(10,5)
    490.3325
    >>> potential_energy(0,0)
    0.0
    >>> potential_energy(2,8)
    156.9064
    >>> potential_energy(20,100)
    19613.3
    """
    if mass < 0:
        # handling of negative values of mass
        raise ValueError("The mass of a body cannot be negative")
    if height < 0:
        # handling of negative values of height
        raise ValueError("The height above the ground cannot be negative")
    return mass * g * height


if __name__ == "__main__":
    from doctest import testmod

    testmod(name="potential_energy")

View on GitHub (pinned to f5988cc097)

Solutions

1. Rebase heights to your reference level: height = y_object - y_reference, ensuring it is >= 0 for the configurations you model
2. If negative heights are meaningful in your reference frame, shift them: height = y - min_y before calling
3. Validate height >= 0 where the data enters your program

Example fix

# before
potential_energy(10, ground_y - object_y)  # negative when object below ground

# after
potential_energy(10, max(0.0, object_y - ground_y))  # or rebase reference explicitly

height = object_y - reference_y  # choose the reference explicitly
if height < 0:
    raise ValueError(f"height above reference must be >= 0, got {height}")
potential_energy(mass, height)

try:
    potential_energy(mass, height)
except ValueError as e:
    if "height" in str(e):
        height = abs(height)  # or rebase the reference level
        potential_energy(mass, height)
    else:
        raise

When it happens

Trigger: potential_energy(10, -5); height computed as y_object - y_ground with operands swapped, or depth/underground positions passed without rebasing to the chosen reference level.

Common situations: World-coordinate systems where ground is not at y=0; choosing a different potential-energy reference level without shifting heights; depth values (below ground, naturally negative) passed as heights.

Related errors

• Gravitational force can not be negative
• Distance can not be negative
• Mass can not be negative
• The length should be non-negative
• The mass of a body cannot be negative

AI-assisted analysis of TheAlgorithms/Python@f5988cc097 (2026-08-14). Data as JSON: /api/errors/59ed49911094eeed. Report an issue: GitHub.