If the mass of a planet is cut in half, how would the force of gravity between that planet and the Sun change? (The force of gravity’s would increase four times; The force of gravity would decrease; The force of gravity would double; The force of gravity would not change)

1 answer

The force of gravity between two objects is described by Newton's Law of Universal Gravitation, which states:

\[ F = G \frac{m_1 m_2}{r^2} \]

where:

  • \( F \) is the force of gravity,
  • \( G \) 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 the centers of the two objects.

If the mass of the planet is cut in half, let's denote the original mass of the planet as \( m_1 \) and the new mass as \( \frac{m_1}{2} \).

The new force of gravity can be expressed as:

\[ F' = G \frac{\left(\frac{m_1}{2}\right) m_2}{r^2} \]

We can see that the new force \( F' \) would be:

\[ F' = \frac{1}{2} G \frac{m_1 m_2}{r^2} = \frac{1}{2} F \]

Thus, when the mass of the planet is cut in half, the force of gravity between that planet and the Sun would decrease.

Therefore, the correct answer is: The force of gravity would decrease.