Question

section d: two-mark questions

1. explain why an astronaut weighs less on the moon than on earth.
2. describe the difference between mass and weight with an example.

Explanation:

1. Weight is the force of gravity acting on an object. The formula for weight is \( W = mg \), where \( m \) is mass and \( g \) is the acceleration due to gravity. The Moon has a smaller mass than Earth, so its gravitational acceleration (\( g_{moon}\approx1.62\ m/s^{2} \)) is less than Earth's (\( g_{earth}\approx9.8\ m/s^{2} \)). Since the astronaut's mass \( m \) remains the same, but \( g \) is smaller on the Moon, using \( W = mg \), the astronaut's weight \( W \) is less on the Moon.
2. Mass is the amount of matter in an object (measured in kilograms, \( kg \)). It is an intrinsic property and does not change with location. For example, a 10 - kg rock has the same mass on Earth and on the Moon. Weight is the force of gravity on an object (\( W=mg \), measured in newtons, \( N \)). A 10 - kg rock has a weight of \( W = 10\times9.8=98\ N \) on Earth and \( W = 10\times1.62 = 16.2\ N \) on the Moon.

Answer:

1. An astronaut weighs less on the Moon than on Earth because weight \( W = mg \). The astronaut's mass \( m \) is constant, but the Moon's gravitational acceleration \( g_{moon}\) (\( \approx1.62\ m/s^{2} \)) is less than Earth's \( g_{earth}\) (\( \approx9.8\ m/s^{2} \)).
2. Mass is the amount of matter (e.g., a 10 - kg rock has the same mass everywhere). Weight (\( W = mg \)) is gravity's force. A 10 - kg rock weighs \( 98\ N \) on Earth (\( g = 9.8\ m/s^{2} \)) and \( 16.2\ N \) on the Moon (\( g = 1.62\ m/s^{2} \)).