Differential equation boundary conditions

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SUMMARY

The discussion focuses on solving the differential equation \(\frac{dN}{dt} = -k_sN^2\) using boundary conditions. The integration process leads to the expression \(-\frac{1}{N} + C = -k_s t\), where the constant \(C\) is defined as \(\frac{1}{N_0}\). This definition arises from applying the boundary condition \(N(0) = N_0\), ensuring that the integration limits are correctly aligned. Understanding this relationship is crucial for accurately solving differential equations with specified initial conditions.

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[tex] \frac{dN}{dt}=-k_sN^2[/tex]

Attempt:

[tex] \frac{1}{N^2}dN = -k_s dt[/tex]

Integrate:

[tex] -\frac{1}{N} + C = -k_s t[/tex]

In the solution manual, C is written [tex]\frac{1}{N_0}[/tex]

Why?
 
Last edited:
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If you integrate from 0 to t on the right, you have to integrate from N0 to Nt on the left, where N0 is the value of N at t = 0.
 
Alternatively use the boundary conditions in this case [itex]N(0)=N_0[/itex] and then solve for C.
 

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