If an astronaut's mass is 70 kg, what will be their weight on the Moon (1/6th of Earth's gravity)?

Correct option is B

The correct answer is (B) 117 N

Explanation:
• To solve this problem, it is necessary to distinguish between mass and weight: mass is an intrinsic property that measures the total amount of matter in an object and remains constant anywhere in the universe, while weight is a variable gravitational force.
• Given that the astronaut's mass is 70 kg, this value does not change when traveling from Earth to the Moon. Weight is calculated using the formula W = m • g, where m is mass and g is the acceleration due to gravity.
• On Earth, using standard gravity (g ≈ 9.8 m/s²), the astronaut's weight is 70 kg • 9.8 m/s² = 686 Newtons (N).
• Since the Moon's gravity is roughly 1/6th of Earth's gravity, the astronaut's lunar weight is calculated by dividing their Earth weight by six: 686 N / 6 ≈ 114.3 N. If using a standard rounding of Earth's gravity to 10 m/s², the calculation becomes (70 • 10) / 6 = 116.66 N, which rounds closely to the provided option of 117 N.

Information Booster:
• Mass is measured in kilograms (kg) using a standard balance scale, whereas weight is a force measured in Newtons (N) using a spring balance scale.
• If an astronaut steps onto the lunar surface, they can jump significantly higher and lift much heavier objects due to the weaker local gravitational pull, despite their physical mass remaining unchanged.
• This difference in gravitational strength is due to the Moon's smaller mass and radius compared to Earth, resulting in a lower surface gravity of approximately 1.62 m/s².

Additional Knowledge:
• 70 N (Option A): An incorrect value that confuses mass units with force units, resulting in an inaccurate calculation of the astronaut's lunar weight.
• 420 N (Option C): This error results from multiplying the mass by six instead of dividing the total weight by the gravity factor of six.
• 686 N (Option D): Represents the astronaut's full weight on the surface of the Earth under standard gravitational conditions before leaving for the Moon.