Minimizing the Functional for the Brachistochrone Problem

In summary, the conversation discusses a functional that needs to be minimized, with +x pointing downward and +y pointing rightward. The homework equations suggest using the Euler-Lagrange equation, but the given solution does not match the expected brachistochrone curve. The person asking for help has attempted to use the equation but is still struggling to find the correct answer. Any assistance would be appreciated.
  • #1
WackStr
19
0

Homework Statement



So if +x points downward and +y points rightwards then the functional that needs to be minimized is:

[tex]\sqrt{2g}T[y]=\int_{x_0}^{x_1}\frac{dx}{\sqrt{x}}\sqrt{1+\left(\frac{dy}{dx}\right)^2}[/tex]


Homework Equations



I think we just have to use the Euler lagrange equation. The book (Hand and Finch says) the solution is:

[tex]y(x)=\sqrt{x(2r-x)}+2r ArcSin\left(\frac{x}{2r}\right)[/tex]

This is not even a brachistrone curve! Am I missing something?
 
Physics news on Phys.org
  • #2
The Attempt at a SolutionI have tried to use the Euler Lagrange equation but I just can't seem to get the answer that is given. Any help would be greatly appreciated!
 

Related to Minimizing the Functional for the Brachistochrone Problem

1. What is the Brachistochrone problem?

The Brachistochrone problem is a mathematical optimization problem that seeks to find the curve between two points that minimizes the time it takes for a particle to travel under the influence of gravity alone. It was first posed by Johann Bernoulli in 1696 and has since been solved using various mathematical techniques.

2. Why is the Brachistochrone problem significant?

The Brachistochrone problem is significant because it played a crucial role in the development of the calculus of variations and the field of mathematical physics. It also has applications in engineering, particularly in the design of roller coasters and other amusement rides.

3. How is the Brachistochrone problem solved?

The Brachistochrone problem can be solved using the calculus of variations, which involves finding the minimum value of a functional. In this case, the functional is the time it takes for the particle to travel between the two points. The solution involves setting up and solving a differential equation known as the Brachistochrone curve.

4. What are some real-world applications of the Brachistochrone problem?

Aside from its applications in roller coaster design, the Brachistochrone problem has also been used in the design of aircraft flight paths, optimization of fuel consumption for spacecraft, and the study of ocean currents. It has also been applied in economics, particularly in the study of consumer preferences and utility maximization.

5. Are there any limitations to the Brachistochrone problem?

One limitation of the Brachistochrone problem is that it assumes a perfect vacuum and ignores air resistance. In real-world situations, air resistance can significantly impact the time it takes for a particle to travel between two points. Additionally, the problem only considers the effect of gravity and does not take into account other forces such as friction or magnetic fields.

Similar threads

  • Advanced Physics Homework Help
Replies
19
Views
952
  • Advanced Physics Homework Help
Replies
8
Views
839
  • Advanced Physics Homework Help
Replies
2
Views
932
  • Advanced Physics Homework Help
Replies
7
Views
2K
  • Advanced Physics Homework Help
Replies
5
Views
843
  • Advanced Physics Homework Help
Replies
9
Views
1K
  • Differential Equations
Replies
2
Views
2K
Replies
4
Views
490
  • Advanced Physics Homework Help
Replies
3
Views
606
  • Advanced Physics Homework Help
Replies
1
Views
964
Back
Top