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.
What is meant by fact that the acceleration due to the gravity of a planet is 9.8 ms-2?
The acceleration due to the gravity of a planet is 9.8 ms-2 means that the velocity of any body freely falling from any height towards the surface of the planet is increasing by 9.8 ms-1 in every second.