Astronomy Practice Exam

According to the Universal Law of Gravitation, attraction between two masses decreases when?

1. The distance between them increases

2. Their sizes increase

3. The temperature rises

4. Their velocities change

The correct answer is: The distance between them increases

The Universal Law of Gravitation states that the force of attraction between two masses is inversely related to the square of the distance between their centers. This means that as the distance between the two masses increases, the gravitational force of attraction decreases. Mathematically, this relation can be expressed by the formula: \[ F = \frac{G \cdot m_1 \cdot m_2}{r^2} \] where \( F \) is the gravitational force, \( G \) is the gravitational constant, \( m_1 \) and \( m_2 \) are the masses, and \( r \) is the distance between the centers of the two masses. Thus, when the distance \( r \) increases, the denominator of the equation becomes larger, resulting in a smaller gravitational force \( F \). Regarding the other options, the size of the masses, changes in temperature, or variations in their velocities do not have a direct impact on the gravitational attraction as influenced by the Universal Law of Gravitation in the context of distance. Specifically, while larger masses do exert greater gravitational force, the crucial factor regarding the decrease in gravitational attraction between two masses is the increasing distance between them.