Answer:
A. Wab > 0.
Explanation:
Work done will be equal to change in gravitational energy in the whole process .
When Masses M₁ and M₂ are initially separated by a distance Ra
their gravitational energy
= - G M₁ M₂ / Ra
When mass M₂ is now moved further away from mass M₁ such that their final separation is Rb
their gravitational energy
= - G M₁ M₂ / Rb
Change in gravitational energy
= - G M₁ M₂ / Rb - ( - G M₁ M₂ / Ra )
= G M₁ M₂ / Ra - - G M₁ M₂ / Rb
= G M₁ M₂ ( 1 / Ra - Rb )
As Ra < Rb
1/Ra > 1 / Rb
So change in gravitational energy is positive
So
Wab > 0.
