How to do the ordinary differential equation? {dA}/{dt}=dotA=-alpha/{2m}A rarr A(t)=A(0)e^{-alpha/{2m}t}

Jamarcus Lindsey

Jamarcus Lindsey

Answered question

2022-09-30

How to do the ordinary differential equation? d A d t = A . = - α 2 m A A ( t ) = A ( 0 ) e - α 2 m t

Answer & Explanation

Demarion Thornton

Demarion Thornton

Beginner2022-10-01Added 11 answers

Given that:
A . = - α 2 m A
Then we can write:
d A d t = - α 2 m A
This is a First-Order linear separable Ordinary Differential Equation, which we can rearrange terms and separate the variables to get:
  1 A   d A =   - α 2 m   d t
Which is directly integrable, to give:
ln | A | = - α 2 m t + C
If we use the suggested initial condition:
A = A ( 0 ) when t = 0
Then:
ln | A ( 0 ) | = 0 + C
Leading to the Particular Solution:
ln | A | = - α 2 m t + ln | A ( 0 ) |
And assuming that A is positive over its range, then:
ln A - ln A ( 0 ) = - α 2 m t
ln ( A A ( 0 ) ) = - α 2 m t
A A ( 0 ) = e - α 2 m t
And finally:
A = A ( 0 ) e - α 2 m t         QED

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