Simpler way to solve differential equation for initial value problem?

Click For Summary
The discussion revolves around solving the differential equation dy/dx = x√y with the initial condition f(3) = 25. The user attempts to separate variables and integrate, ultimately deriving the solution y = (1/4 x^2 + 11/4)^2. Other participants confirm the correctness of the solution and note that the variable separation method used is appropriate. There is a consensus that there are no simpler methods for integrating this particular differential equation. The conversation highlights the effectiveness of the chosen approach in solving the initial value problem.
kreil
Science Advisor
Insights Author
Messages
665
Reaction score
68
Rewrite the differential equation \frac{dy}{dx}=x{\sqrt{y}} in the form y=f(x) given the initial condition f(3)=25.

I am new to integration so I am unsure about my work on this problem.

\frac{dy}{dx}=x{\sqrt{y}}

dy=(dx)(x)(\sqrt{y})

\frac{dy}{\sqrt{y}}=(dx)(x)

\int{\frac{dy}{\sqrt{y}}}=\int{(x)(dx)}

2y^{\frac{1}{2}}=\frac{1}{2}x^2+ C

10=\frac{9}{2}+C

C=\frac{11}{2}

2y^{\frac{1}{2}}=\frac{1}{2}x^2+\frac{11}{2}

y=(\frac{1}{4}x^2+\frac{11}{4})^2

If I did it correctly, is there an easier way to do it? If I messed up, where?

Thanks
 
Physics news on Phys.org
Looks right to me.

It doesn't seem like that much work to me.
 
No, it's not a lot of work, I just thought that there might be others ways to arrive at the same answer.

Thanks
 
kreil said:
No, it's not a lot of work, I just thought that there might be others ways to arrive at the same answer.
Thanks

Nope,there's no simpler way to integrate that diff.eq. than the variable separation method.
Nice work!

Daniel.
 
Thread 'Correct statement about size of wire to produce larger extension'
The answer is (B) but I don't really understand why. Based on formula of Young Modulus: $$x=\frac{FL}{AE}$$ The second wire made of the same material so it means they have same Young Modulus. Larger extension means larger value of ##x## so to get larger value of ##x## we can increase ##F## and ##L## and decrease ##A## I am not sure whether there is change in ##F## for first and second wire so I will just assume ##F## does not change. It leaves (B) and (C) as possible options so why is (C)...

Similar threads

  • · Replies 3 ·
Replies
3
Views
829
  • · Replies 18 ·
Replies
18
Views
1K
Replies
6
Views
4K
  • · Replies 2 ·
Replies
2
Views
855
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 19 ·
Replies
19
Views
2K
Replies
42
Views
3K
  • · Replies 7 ·
Replies
7
Views
765
Replies
7
Views
1K
  • · Replies 3 ·
Replies
3
Views
519