Question

select the correct answer.

with all his gear, neil armstrong weighed 360 pounds on earth. when he landed on the moon, he weighed 60 pounds. why?

• his mass changed while traveling to the moon.
• the gravity on the moon is six times the gravity on earth.
• the gravity on the moon is less than the gravity on earth.
• he experienced the effects of a gravity slingshot.

Explanation:

Analyze the relationship between mass and weight

The concept of weight is directly related to the Gravitational Force Factors acting on an object. Mass is an intrinsic property of matter that does not change regardless of location, whereas weight is the gravitational force exerted on that mass:

$$ W = m \cdot g $$

where \(W\) is weight, \(m\) is mass, and \(g\) is the local gravitational acceleration.

Compare gravity on Earth and the Moon

Neil Armstrong's mass remained constant during his journey. His weight decreased from 360 pounds on Earth to 60 pounds on the Moon because the Moon has a smaller mass and radius than Earth, resulting in a weaker surface gravity. Specifically, the Moon's gravity is about one-sixth (\(\frac{1}{6}\)) of Earth's gravity:

$$ g_{\text{Moon}} \approx \frac{1}{6} g_{\text{Earth}} $$

Evaluate the given options

• Option 1: "His mass changed while traveling to the Moon." This is incorrect because mass is constant.
• Option 2: "The gravity on the Moon is six times the gravity on Earth." This is incorrect because the Moon's gravity is weaker, not stronger.
• Option 3: "The gravity on the Moon is less than the gravity on Earth." This is correct because a lower gravitational acceleration results in a lower measured weight (\(60\text{ lbs} < 360\text{ lbs}\)).
• Option 4: "He experienced the effects of a gravity slingshot." This is irrelevant to his static weight on the lunar surface.

Answer:

• His mass changed while traveling to the Moon.
• The gravity on the Moon is six times the gravity on Earth.
• The gravity on the Moon is less than the gravity on Earth. (Correct answer)
• He experienced the effects of a gravity slingshot.