Question

The earth is able to retain its atmosphere because of _____

(a) the mean velocities of atmospheric gas molecules which is less than that of the earth’s escape velocity

(b) the mean velocities of atmospheric gas molecules which is greater than that of the earth’s escape velocity

(c) the gravitational effect of the moon

(d) the earth’s magnetic field

The question was posed to me in homework.

Question is from Gravitation in chapter Gravitation of Physics – Class 11

Answer 1

The correct option is (a) the mean velocities of atmospheric gas molecules which is less than that of the earth’s escape velocity

For explanation: The escape velocity of earth is approximately 11.2km/s. This is greater than the root-mean-square velocities of the atmospheric gases. Hence, the gases are unable to escape into the vacuum of space.