Question

Please help me solve this question...
Two point masses m and M are separated by a distance d.A third point mass along the line joining m and M experiences no gravitational force.What is the distance of the third point mass from m?

Answer 1

Let's call the mass of the third point m' and the distance from it to m, d'.

The only way that the 3rd point mass can experience no gravitational force is if it is somewhere between m and M. You can imagine that if m and M are equal and they both pull on m' with equal force, then d' must be at the center (i.e. d/2). If M were bigger then d' would need to be smaller.

You'll need to find the force of m on m' and the force of M on m' and set them equal to each other and solve for d'.

Does this make sense?