8 not counting Pluto 9 if counting Pluto, Pluto is technically not a planet anymore so best dentures 8.
Well you see friction works by you moving in motion so why not try that.
The Earth's atmosphere is kept close to Earth by gravity. Just as the Earth's gravity keeps you firmly on the ground, it also acts on the gases of the Earth's atmosphere, holding it in place and allowing us to breathe.
Answer:

Explanation:
Given that,
The velocity of an astronaut in a circular path, v = 16 m/s
The radius of the accelerator, r = 8 m
We need to find his centripetal acceleration. The formula that is used to find the centripetal acceleration is given by :

So, the required centripetal acceleration is
.