CBSE Class 11-science Answered
Escape velocity is the velocity required to be given to the object so that
the object is moved far away from earth's gravitational field .
Let ve be the escape velocity given to the object
Total energy E of the object on earth surface is sum of its kinetic energy and potential energy .
...............................(1)
First term in above expression is kinetic energy and second term is potential energy
m is mass of object , G is universal gravitational constant , M is mass of earth and R is radius of earth.
When the object is noved to infinite distance far away from earth;s gravitatioal field ,
its potential energy is zero and it has negligible kinetic energy .
hence we can consider total energy E∞ at infinite distance is zero.
By conservation of energy
E = E∞ = 0
Hence , from eqn.(1) , we get
by substituting g = 9.8 m /s2 and radius of earth R = 6371 km = 6.371 m , we get
ve = 11.2 km/s