Academic Master


Using levers to examine the Ruler Balance mechanism 

From the observations after balancing the two rulers (one shorter and another one longer), it is observed that a shorter ruler balances faster than a longer ruler. This is due to the effects of the force of gravity on the rulers, plus other factors, including the effort and load distance.  Effort distance can be considered from the fulcrum or the turning point (the finger) to one end of the ruler. Similarly, the load distance can be considered from the finger (turning point) to the other opposite end of the ruler (Mayer-König, 2017). The physics behind these mechanisms can be explained physically using a lever.

Levers are all over within us. This ranges widely from seesaws to balancing a ruler on the finger. This phenomenon can be explained in physical terms. This is because the fundamental physics principles are the ones that make the two rulers balance.

A lever can be thought of as an easy mechanism that has two underlying components: a solid rod, which is the ruler, in this case, the pivot, also known as the fulcrum, the finger represents this, the input force (effort), and the force of output, (the load). The ruler was stationed so that part rested on the finger (fulcrum). This fulcrum must be in the stationary position.

When a force is applied along the ruler’s length, the ruler pivots (rotates) around the fulcrum. It thus exerts the output force on some part of an object that needs to move. The ruler balances at the fulcrum when the input force equals the force of the output. In physical terms, it is stated that the ruler balances when the force of action is equal to the force of reaction.

This experiment is used in our day-to-day activities. For instance, this technique has been used throughout the history of measurements, specifically in weighing objects. If the distance from the fulcrum is equal to that of the other, the lever and the ruler, in this case, will balance out if the weights are of similar mass(Jerdén,2016). If the known weight is used on one end, the unknown weight on the opposite can be easily determined. This situation becomes captivating when the distances from the pivot (the finger) are the same. In this case, there is an interesting formula, a mathematical relationship between the product of the mass and the distance on both sides of the ruler (lever).

The shorter ruler balances faster. This is primarily because the effort distance (or load distance) is short, thus putting little weight on the ruler. This little overall weight is the one that makes it possible for the ruler to balance faster (YaLin Shi, 2017). In addition, the smaller ruler’s small mass (less weight) gives it more ability to balance faster than a larger, longer, heavier ruler. This is because it experiences little force of gravity, hence balancing faster than the longer ruler. It has a larger mass, hence more force of gravity. Thus, it takes time to balance. One has to take a lot of time, adjusting it now and then to balance.


Mayer-König, B. 2017. Popular physics: Encounter with mechanisms of science (16), pp.26-40.

Jerdén, B., 2016. Mechanisms of physical education and analysis. The professional view of levers and the underlying principles 38(3), pp.327-3632.

YaLin Shi(2017).World theory of science. Journal scientists on discoveries and Communication64(4), 602-734.



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