First order ODE initial value problem

In summary, the conversation discusses finding a fourth order polynomial with a given initial condition and a first order differential equation. One individual suggests disregarding the initial value condition and solving for y = t^4, while another suggests integrating the differential equation and solving for the initial value. They also mention that there may be multiple solutions to the equation.
  • #1
Shade
13
0

Homework Statement



Given the below stated equations I need to find the exact polynomial given the initial condition.

y(0) = 1
y = 4*t*sqrt(y)

Homework Equations

The Attempt at a Solution



I simply disregard the initial value condition and get y = t^4

How can I find the fourth order polynomial with the given initial value?

( see also a former thread https://www.physicsforums.com/showthread.php?t=111094 )
 
Physics news on Phys.org
  • #2
Is it not possible to integrate a first order differential equation and also consider the initial value y(0) = 1 ?
 
  • #3
Isn't there a typo? Where is y' ?
 
  • #4
I assume the equation is written y'=4ty^(1/2) in which case it appears you have dy/dt=y' and this is a seperable equation. Solve for y and then solve for the initial value.
 
  • #5
Shade said:

Homework Statement



Given the below stated equations I need to find the exact polynomial given the initial condition.

y(0) = 1
y = 4*t*sqrt(y)

Homework Equations




The Attempt at a Solution



I simply disregard the initial value condition and get y = t^4

How can I find the fourth order polynomial with the given initial value?

( see also a former thread https://www.physicsforums.com/showthread.php?t=111094 )

I can see any "attempt at a solution". Saying "I simply disregard the initial value condition and get y = t^4" makes no sense! How did you "get y= t^4"? Don't you have to integrate somewhere and doesn't that introduce a "constant of integration?

The differential equation is [itex]\frac{dy}{dt}= 4t\sqrt{y}= 4ty^{\frac{1}{2}}[/itex]

That can be written [itex]y^{-\frac{1}{2}}dy= 4t dt[/itex]. Now integrate both sides.

It's interesting that there are two distinct solutions (actually, there are an infinite number of solutions). The "uniqueness" part of the "existance and uniquenss" theorem is not satisfied.
 

1. What is a first order ODE initial value problem?

A first order ordinary differential equation (ODE) initial value problem is a type of mathematical problem that involves finding a function that satisfies a given differential equation and also satisfies a set of initial conditions, usually in the form of a starting point or a starting value for the function. The solution to the problem is a function that describes the behavior of a dependent variable over a continuous range of independent variables.

2. What are some common techniques for solving first order ODE initial value problems?

Some common techniques for solving first order ODE initial value problems include separation of variables, integrating factors, substitution methods, and using power series or numerical methods. The specific technique used depends on the form of the ODE and the initial conditions given.

3. Why are initial value problems important in mathematical modeling?

Initial value problems are important in mathematical modeling because they allow us to describe and predict the behavior of a system over time. By solving the initial value problem, we can determine the values of the dependent variable at any point in the independent variable's range, which is essential for understanding and analyzing real-world systems.

4. Can all first order ODEs be solved analytically?

No, not all first order ODEs can be solved analytically. Some ODEs have no closed form solution, meaning they cannot be expressed in terms of elementary functions. In these cases, numerical methods or approximations are used to find a solution.

5. What are some real-world applications of first order ODE initial value problems?

First order ODE initial value problems have many real-world applications, such as modeling population growth, chemical reactions, and electrical circuits. They are also used in engineering, physics, and economics to describe and predict the behavior of various systems over time.

Similar threads

  • Calculus and Beyond Homework Help
Replies
3
Views
566
  • Calculus and Beyond Homework Help
Replies
11
Views
956
  • Calculus and Beyond Homework Help
Replies
8
Views
758
Replies
5
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
699
  • Calculus and Beyond Homework Help
Replies
9
Views
1K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
6
Views
284
  • Calculus and Beyond Homework Help
Replies
12
Views
1K
  • Calculus and Beyond Homework Help
Replies
8
Views
2K
Back
Top