Weight of a body is less in the mines. Why?
The weight of a body is less in the mines because when we move deeper the earth gravity decreases but our mass is always constant.
Why G is a universal gravitational constant?
We all know that G is the force of attraction between 2 bodies each of mass 1 kg and kept at a distance of 1m between their centers. It is a constant value that is measured in a vacuum and is the same in the whole universe. So, G is a universal gravitational constant.