Advertisements
Advertisements
प्रश्न
Explain why there is no atmosphere on moon.
Advertisements
उत्तर
The moon has a small gravitational force (pull) and hence, the escape velocity is small. The value of escape velocity for the moon is 4.6 km/s.
As the moon is in the proximity of the earth as seen from the sun, the moon has the same amount of heat per unit area as that of the earth.
The air molecules have a large range of speeds. Even though the rms speed of the air molecules is smaller than the escape velocity on the moon, a significant number of molecules have speeds greater than escape velocity and they escape.
Now, the rest of the molecules arrange the speed distribution for the equilibrium temperature. Again a significant number of molecules escape as their speed exceeds the escape speed. Hence, over a long time, the moon has lost most of its atmosphere.
At 300 K, `V_(rms) = sqrt((3kT)/m)`
= `sqrt((3 xx 1.38 xx 10^-23 xx 300)/(7.3 xx 10^-26)`
= 1.7 km/s
Vesc for moon = 4.6 km/s ......[Vesc = escape velocity]
APPEARS IN
संबंधित प्रश्न
Do you expect the gas in a cooking gas cylinder to obey the ideal gas equation?
Comment on the following statement: the temperature of all the molecules in a sample of a gas is the same.
It is said that the assumptions of kinetic theory are good for gases having low densities. Suppose a container is so evacuated that only one molecule is left in it. Which of the assumptions of kinetic theory will not be valid for such a situation? Can we assign a temperature to this gas?
A gas is kept in an enclosure. The pressure of the gas is reduced by pumping out some gas. Will the temperature of the gas decrease by Charles's low?
If the molecules were not allowed to collide among themselves, would you expect more evaporation or less evaporation?
Which of the following quantities is the same for all ideal gases at the same temperature?
(a) The kinetic energy of 1 mole
(b) The kinetic energy of 1 g
(c) The number of molecules in 1 mole
(d) The number of molecules in 1 g
During an experiment, an ideal gas is found to obey an additional law pV2 = constant. The gas is initially at a temperature T and volume V. Find the temperature when it expands to a volume 2V.
Use R = 8.3 J K-1 mol-1
The weather report reads, "Temperature 20°C : Relative humidity 100%". What is the dew point?
The condition of air in a closed room is described as follows. Temperature = 25°C, relative humidity = 60%, pressure = 104 kPa. If all the water vapour is removed from the room without changing the temperature, what will be the new pressure? The saturation vapour pressure at 25°C − 3.2 kPa.
Answer in brief:
What will happen to the mean square speed of the molecules of a gas if the temperature of the gas increases?
Calculate the ratio of the mean square speeds of molecules of a gas at 30 K and 120 K.
Average kinetic energy of H2 molecule at 300K is 'E'. At the same temperature, average kinetic energy of O2 molecule will be ______.
A cylinder containing an ideal gas is in vertical position and has a piston of mass M that is able to move up or down without friction (Figure). If the temperature is increased ______.
Two gases A and B are at absolute temperatures of 360 K and 420 K, respectively. The ratio of the average kinetic energy of the molecules of gas B to that of gas A is ______.
Assuming the expression for the pressure P exerted by an ideal gas, prove that the kinetic energy per unit volume of the gas is `3/2` P.
Which of the following materials is diathermanous?
Show that the average energy per molecule is directly proportional to the absolute temperature ‘T’ of the gas.
