Advertisements
Advertisements
प्रश्न
Explain why there is no atmosphere on moon.
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
The process on an ideal gas, shown in figure, is
The mean speed of the molecules of a hydrogen sample equals the mean speed of the molecules of a helium sample. Calculate the ratio of the temperature of the hydrogen sample to the temperature of the helium sample.
Use R = 8.314 JK-1 mol-1
At what temperature the mean speed of the molecules of hydrogen gas equals the escape speed from the earth?
Use R = 8.314 JK-1 mol-1
One mole of an ideal gas undergoes a process `P = (P_0)/(1+(V/V_0)^2` where `p_0` and `V_0` are constants . Find the temperature of the gas when `V=V_0` .
The average translational kinetic energy of gas molecules depends on ____________.
When photons of energy hv fall on a metal plate of work function 'W0', photoelectrons of maximum kinetic energy 'K' are ejected. If the frequency of the radiation is doubled, the maximum kinetic energy of the ejected photoelectrons will be ______.
The average translational kinetic energy of a molecule in a gas becomes equal to 0.49 eV at a temperature about (Boltzmann constant = 1.38 x 10-23 JK-1) ____________.
Average kinetic energy of H2 molecule at 300K is 'E'. At the same temperature, average kinetic energy of O2 molecule will be ______.
A molecule consists of two atoms each of mass 'm' and separated by a distance 'd'. At room temperature the average rotational kinetic energy is 'E', then its angular frequency 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.
