The amount of movement of the particles depends on the amount of acting on them and their relationship to other atoms.

The amount of movement of the particles depends on the amount of force acting on them and their relationship to other atoms.

Explanation:

The inter-atomic force determines the inter-atomic distance which governs the amount of movement of the particles.

For example in solids, the inter-atomic force is stronger and hence, the distance between any atoms is very very small which restricts the movement of the particles. On the other hand, in case of liquids and gases, the inter-atomic forces are not very strong and there is more distance between the atoms which allows free movement of particles.

It's either the weight of the brick or else the tension in the rope.  Show us the diagram and we'll know for sure.