Moon is the only satellite of earth. Mass of moon is very much lower than that of earth. Is there any difference in gravitational force of moon and earth? Explain.

Moon is the only satellite of earth. Mass of moon is very much lower than that of earth. A girl argues that even today if we visit moon, we can see the foot steps of Neil Armstrong. What is your opinion?

A person in an artificial satellite of the earth experiences weightlessness. The moon is a natural satellite of the earth. A satellite is revolving very close to the earth. What is the percentage increase in velocity needed to make it escape from the gravitational field of the earth?

Give justification, Graphite is a better lubricant on moon than that on earth.