a scientist designs an experiment that requires two atomic particles whose only fundamental force exerted between them is the gravitational force. Which combination of particles and separation distance will meet this condition?

A proton and neutron located 1.0 mm apart

Explanation:

As we know, atoms are composed of fundamental particles, atomic particles: protons, neutrals and electrons.

Protons and neutrons are found in the nucleus of the atom and are located very close to each other. The electrons, however, are located in the electrosphere, a little further away from the nucleus and consequently, away from the protons and neutrals, by approximately 1.0 mm. In addition, the only force that acts between protons and neutrals is the gravitational force, which is very important, even, so that the electrodes are not attracted over the nucleus.

For this reason, we can confirm that the combination of particles and separation distance that will meet the condition shown in the question above are: a proton and neutron located 1.0 mm apart.

Infinite distance; all objects in the universe.

Explanation:

In physics, there are four fundamental interactions, and the fundamental interactions include strong force, electromagnetic force, weak force and gravitational force. These forces governs how objects or particles interact and how certain particles decay.

With respect to their relative strengths, the strong force is regarded as the most powerful, followed by the electromagnetic force, the weak force, and the gravitational force.

Gravitational force and electromagnetic force operates at infinite distance. Gravitational force acts between all objects of the universe, no matter the distance/how far the body are apart.