Question

Derive an expression for binding energy of a body at rest on the earth's surface.

Answer 1

consider a body of mass ‘ m ’ which is rest on the surface of the earth. as it is in rest so, it cannot possess kinetic energy e.g., K.E = 0

because body is in the gravitational field of the earth so, gravitational potential at a point the surface of the earth is given by $V=-\frac{GM}{R}$

now, potential energy = gravitational potential × mass of body
= $-\frac{GMm}{R}$
now, total mechanical energy is $T.E=K.E+P.E$
so, $T.E=-\frac{GMm}{R}$
here negative sign indicates that the body is bound to the earth by attractive force and cannot leave it on its own. To move the body to infinity , we have to supply energy from outside the body - planet system. this energy is known as binding energy.
so, binding energy $E_r=\frac{GMm}{R}$

Answer 2

Answer:

previous ans is absolutely correct