Question

two objects A and B having masses 2 kg and 4 kg respectively are separated by 2m where should an object of mass 1 kg be kept such that the gravitational force on the object due to object A and B is zero​

Answer 1

Gravitational force between two objects can only be zero if they are in contact with each other.

In other words, the distances between them should be zero.

Hence this is the answer.

r=0