Question

i)why do astronauts in moon feel weightless? ii ) what keeps the moon in uniform circular motion?

Answer 1

Astronauts at moon feel weightless because the gravitational field at moon is very weak(about 1/6 of the earth) therefore it does not attract other bodies such as humans with tha same pull as earth does..
Now, Moon keeps performing Uniform Circular Motion around the earth by the virtue of the
Gravitational force between the earth and the moon.. This force provides the necessary centripetal acceleration for its uniform motion..
Hope it helps..

Answer 2

(i) Because the gravity of the moon is very less to compare to that of earth. weight=mg. weight depends on gravity or weight is directly proportional to gravity and Mass of the body.
(ii) The earth's gravity acts as a centripetal force to the moon when the moon moves it experiences a centrifugal force to keep moving in uniform circular motion