Answer: The ball would exert and equal force on the astronaut in the opposite direction. Both would move away from each other in a straight path. Hope this helps!
A single pulley has no advantage in reducing force. A single pulley only helps by changing direction of effort, pulling something from up to down feels easier then vice versa due to our muscles arrangement. However, the force needed is the same.
Meanwhile multiple pullies divide the tension. The lower pulley itself reduces the force into half so as to you feel a part of the tension while rest is suspended by the ceiling in the case in the diagram below.
Answer:
A centripetal force (latin: towards the center) is a force shown in any motion that does NOT go in a straight line, related to the fact that your velocity vector changes in direction, and thus you have an acceleration that goes in the same direction - adding an image for more clarity. Rest is just having to remember that acceleration and the force that causes it have the same direction, as do acceleration and change in velocity.
Centrifugal force (latin again: away from the center) is an apparent force, related to the fact that bodies have a tendency - called inertia - of wanting to keep their state of straight motion (or stillness, in case they're not moving to begin with). The moment they get accelerated in a curved trajectory (think a ball on the back seat of a car rolling to the outer side of the curve, you yourself being pushed towards the door if someone drives quite aggressively, or if you are into flight, the ball in a steam gauge turn coordinator, the internet should have photos of it), they receive an apparent acceleration relative to the frame of the moving place where they are, while they try to keep thier relative motion compared to an inertial frame of reference (ie, the rest of the earth).
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297.729km :-) hope this helps