The masses and radii of the earth and moon are M1,R1 and M2,R2 respectively. Their centres are distance d apart. The minimum velocity with which a particle of mass m should be projected from a point midway between their centres so that it escapes to infinity is
2√Gd(M1+M2)
Gravitational potential at mid point
V=−GM1d2+−GM2d2
Now, PE=m×V=frac−2Gmd(M1+M2)
[m = mass of particle]
So, for projecting particle from mid point to infinity
KE=|PE|
⇒12mv2=2GMd(M1+M2)⇒v=2√G(M1+M2)d