Critical value refers to the condition that a physical quantity must meet when an object changes from one physical state to another, which is equivalent to stagnation point in mathematics.

Therefore, using the critical state to solve the maximum and minimum values of physical quantities has become an important method to solve the maximum value in physics. Some people think that it is prudent to solve the maximum value with critical state, and the relationship between the two States should be distinguished first.

Extended data:

There are many examples of critical values in physics, such as the voltage on the capacitor when the capacitor is charged and discharged, and the speed at which raindrops are resisted by f=-kv. Some scholars have studied that their motion laws are similar.

That is, the physical quantities to be changed are all chain feedback changes and follow the first-order linear differential equation. Because there is a critical point and it is easy to determine, it is often mistaken for the maximum value, but in fact there is no maximum value, so it can only be considered as the existence of the maximum value and equal to its critical value in approximate cases.