My name is Alexander FufaeV and here I write about:
Law of the Lever: How to Lift a Heavy Object with One Finger
Important Formula
$$\class{green}{F_1} \, \class{green}{l_1} ~=~ \class{blue}{F_2} \, \class{blue}{l_2}$$
$$F_1 ~=~ \frac{ F_2 \, l_2 }{ l_1 }$$
$$l_1 ~=~ \frac{ F_2 \, l_2 }{ F_1 }$$
$$F_2 ~=~ \frac{ F_1 \, l_1 }{ l_2 }$$
$$l_2 ~=~ \frac{ F_1 \, l_1 }{ F_2 }$$
What do the formula symbols mean?
Effort force
$$ F_1 $$ Unit $$ \mathrm{N} = \frac{\mathrm{kg} \, \mathrm{m}}{\mathrm{s}^2} $$
Force acting on the effort arm. Effort arm is a part of the lever. If a force is applied to the effort arm, the load arm with a mass on it is lifted.
Effort arm length
$$ l_1 $$ Unit $$ \mathrm{m} $$
Length of the effort arm is the length measured from the point of application of the effort force to the pivot point.
Load force
$$ F_2 $$ Unit $$ \mathrm{N} $$
Load force is a force acting on the load arm. Load arm is the part of the lever on which, for example, the mass to be lifted is placed. In this case, the load force \(F_2\) corresponds to gravity force.
Load arm length
$$ l_2 $$ Unit $$ \mathrm{m} $$
Length of the load arm measured from the point of application of the force \(F_2\) to the pivot point.
The law of the lever demonstrated on a seesaw. Shown in green is the part of the lever called the force arm. And shown in blue is the part of the lever called the load arm. The force arm has length \(l_1\), measured to the pivot point (shown in red). And the load arm has the length \(l_2\).
There is a mass on the load arm that is subjected to a force \(F_2\). This can be, for example, the gravitational force that pulls the mass to the ground. To lift the mass on the seesaw, we must act on the force arm with a force \(F_1\). The longer the force arm, the smaller this force \(F_1\) must be. This means that it is easier to lift a mass with a longer force arm. This is the law of leverage. As a formula, we can write it as follows:
$$ \begin{align} \class{green}{F_1} \, \class{green}{l_1} ~=~ \class{blue}{F_2} \, \class{blue}{l_2} \end{align} $$