The Moon has a smaller mass, resulting in a weaker gravitational pull.
Explanation
Weight is defined as the force with which a celestial body attracts an object towards its center. It is mathematically expressed as W = mg, where m is the mass of the object and g is the acceleration due to gravity. The value of g depends on the mass (M) and radius (R) of the celestial body according to the formula:
g = GM / R²
where G is the universal gravitational constant.
Option Analysis
- The Moon possesses no atmosphere to exert pressure. is incorrect: The presence or absence of an atmosphere affects atmospheric pressure and buoyancy, but it does not determine the gravitational force (weight) exerted by the celestial body.
- The Moon has a smaller mass, resulting in a weaker gravitational pull. is correct: The Moon has a significantly smaller mass compared to the Earth (approximately 1/81 of Earth's mass). Although the Moon's radius is also smaller, the substantial difference in mass results in a weaker gravitational pull. Consequently, the acceleration due to gravity on the Moon is approximately 1/6th of that on Earth. Since weight is directly proportional to gravity (W ∝ g), an object weighs less on the Moon.
- The distance between the object and the Moon's center is greater. is incorrect: The radius of the Moon is smaller than the radius of the Earth. Therefore, an object on the Moon's surface is actually closer to the Moon's center than an object on Earth's surface is to Earth's center. If the masses were equal, this would result in higher gravity; however, the Moon's low mass overrides this factor.
- The mass of the object decreases in a low-gravity environment. is incorrect: Mass is an intrinsic property of matter representing the quantity of matter in an object. It remains constant regardless of location or gravitational environment. Only weight changes.
Key Takeaway
Mass is constant everywhere in the universe, whereas weight varies depending on the local gravitational field strength. The Moon's gravity is weaker primarily because its mass is much smaller than Earth's.