How does an astronaut's inertia on earth compare to his inertia in space, where he experiences little to no gravitational forces?

The sun’s mass is 2.0×10^ 30 kg, its radius is 7.0×10 5 km, and it has a rotational period of approximately 28 days. if the sun should collapse into a white dwarf of radius 3.5×10 3 km, what would its period be if no mass were ejected and a sphere of uniform density can model the sun both before and after?

What is friction? how does it affect the motion of an object?

Why do different substances have diffrent properties