The force of gravity between two objects is described by Newton's law of universal gravitation, which states that the force of gravity \( F \) is given by the equation:
\[ F = G \frac{m_1 m_2}{r^2} \]
where:
- \( F \) is the gravitational force,
- \( G \) is the gravitational constant,
- \( m_1 \) and \( m_2 \) are the masses of the two objects (in this case, the planet and the Sun),
- \( r \) is the distance between their centers.
If the mass of the planet is cut in half, then the force of gravity will also be half of what it was, assuming the mass of the Sun and the distance \( r \) remain unchanged.
Therefore, the correct response is:
The force of gravity would decrease.