What is earthing?

What do you mean by earthing ?

What is the thickness of the ozone layer over the Earth surface?

What is the main source of energy for all ecosystem on earth?

A body weighs 63 N on the surface of the earth. What is the gravitational force on it due to the earth at a height equal to half the radius of the earth ?

An apple falls because of the gravitational attraction of earth. What is the gravitational attraction of apple on the earth?

An object weight 72 N the Earth. What its weight at a height R/2 from Earth.

The Moon subtends an angle of 1^(@) 55' at the base line equal to the diameter of the Earth. What is the distance of the Moon from the Earth? (Radius of the Earth is 6.4 xx 10^(6) m)

As you have learnt in the text, a geostationary satellite orbits the earth at a height of nearly 36,000 km from the surface of the earth. What is the potential due to earth’s gravity at the site of this satellite ? (Take the potential energy at infinity to be zero). Mass of the earth = 6.0 xx 10^(24) kg." radius" = 6400 km .