Question

why does not the air of earth go into space

Answer 1

Earth is a massive planet having a high gravitational force. This force is responsible for holding the atmosphere to the earth and prevents the air from escaping into the outer space.Momentum = mass *velocityAlso mechanical energy = potential energy + kinetic energyKinetic energy = ½ mv2 where m is mass and v is the velocityNow if v = 0 then kinetic energy is 0.But potential energy = mass * acceleration due to gravity * heightAs there may be some height attained by the body,there may be some potential energy , as a result, the mechanical energy may not be 0 even if the kinetic energy is 0.