Two or more pulleys used together constitute a block and tackle which, unlike a fixed pulley, does impart mechanical advantage as a function of the number of pulleys that make up the arrangement. So, for example, a block and tackle with three pulleys would have a mechanical advantage of three.

Collinear forces act along the same line of action, concurrent forces pass through a common point and coplanar forces act in a common plane.

Mechanics deals with motion and the forces that produce motion.

Normal force (F_N) represents the force a surface exerts when an object presses against it.

Potential energy is the energy of an object by virtue of its position relative to other objects. It is energy that has the potential to be converted into kinetic energy.