The frictional force acting on a body placed on a horizontal plane is
$F=\mu{R}$
where $R$ is the normal reaction and is equal to weight of a body in this case. And $\mu$ is the coefficient of friction. But, if gravity is zero, then is the frictional force zero (ignoring all other friction due to atmosphere etc.)? If friction is zero, then how do astronauts in a spaceship experiencing zero gravity move?
(I saw so many question related to this on this site, but they give explanations on cosmological effects on it. But I here avoid all such effects and I want answer to only this specific question.)
Best Answer
The normal reaction force is not necessarily equal to weight. When you jump, you push down on the ground. That pushing force plus your weight result in a normal reaction force larger than your weight, which is why you are propelled off the ground.
For astronauts in a space ship, they can push against a wall to generate the normal force necessary for friction (or traction) to allow them to propel themselves parallel to the wall. They necessarily push themselves away from the wall at the same time, so they would need to use multiple walls to move from one place to another.
If you watch a video of astronauts on the International Space Station, you'll see that every spare section of wall has hand holds to allow for easier movement because of the reduced friction.