Answer:
The force between two objects is calculated through the equation,
F = Gm₁m₂/d²
where m₁ and m₂ are the masses of the objects. In this case, an unknown mass and Earth. d is the distance between them and G is the universal gravitation constant.
In the second case, if the force is to become 2.5 times the original and all the variables are constant except d then,
2.5F = Gm₁m₂ / (D²)
D = 0.623d
Subsituting the known value of d,
D = 0.623(6.9 x 10^8) = 4.298 x 10^8 m
Wow your question looks crazy, the answer is that there IS a force on the book, there always is! Atleast when you're on earth anyways, but why is there no work being done? Because it's not moving. Which sounds like 3 to me.
But I want you to understand this, W = Fdcos(x), there's no distance here, so the W = 0
Typical examples of inelastic collision are between cars, airlines, trains, etc.
For instance, when two trains collide, the kinetic energy of each train is transformed into heat, which explains why, most of the times, there is a fire after a collision. However, the momentum of the two trains that are involved in the collision remains unaffected. So, the trains collide with all their speed, maintaining their momentum, yet their kinetic energy is transformed into heat energy.
Another way to explain a train or a car collision is this: when the two trains or cars collide, they stick together while slowing down. They slow down because their kinetic energy is gradually lost. Still, they collide because they conserve their momentum.
I believe it's A. Sorry if I'm incorrect.