Question

The acceleration due to gravity g on Earth’s surface is about 9.81 m/s2. Using the universal law of gravitation calculate g as experienced by an astronaut on the ISS, orbiting at average altitude of 415km.

What is the weight of a 60kg astronaut on the ISS?
Why does the astronaut experience ‘weightless’ even if her weight in far from being zero?

Answer 1

Universal law of gravitation :

Gravitaional force on a mass due to another mass at a distance is

On the surface of earth, acceleration due to gravity is

where radius of earth

Acceleration due to gravity at an altitude is

Weight of person (force of gravitational attraction) on ISS  

Apparent weight of a person is obtained from Normal reaction due to person on a weighing machine.

In this case both weighing machine and person are in orbit which is same thing as free fall

since they have an acceleration

Since Normal reaction is zero, astronaut experiences weightless ness even though gravitational attaction is not zero.