An astronaut has a mass of 84 kg. Calculate his weight on Earth and on the Earth’s moon (g moon = 1.6 m/s2). Does his mass change when he goes from Earth to its moon?

Answer 1

A simple definition of mass is the amount of matter an object is made of, this number does not change when the acceleration due to gravity changes, so this means that the astronaut's mass remains 84kg regardless of the acceleration due to gravity.

The weight of an object is also known as the force due to gravity on the object. This means we can calculate weight using the equation Weight = Acceleration due to gravity x Mass, or F = mg.

Weight of the Astronaut on the Earth:

g_earth = 9.81 m/s^2 downwards

m_astronaut = 84 kg

Weight_Earth = m_astronaut x g_earth = 84kg * 9.81m/s^2 = 824.04 Newtons

Weight of the Astronaut on the Moon:

g_moon = 1.6 m/s^2 downwards

m_astronaut = 84 kg

Weight_moon = m_astronaut x g_moon = 84kg * 1.6m/s^2 = 134.4 Newtons