Differential equations time evolution

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SUMMARY

The discussion focuses on solving differential equations related to time evolution in a mechanics assignment from a physics class. Participants emphasize the importance of eliminating all derivatives of the variable y to form a second-order equation solely in terms of x and its time derivatives. The solution involves differentiating the equation for dx/dt to derive d²x/dt² and substituting derivatives appropriately to eliminate y. The conversation highlights the necessity of understanding various methods for solving differential equations, as well as the importance of posting in the correct forum for specific topics.

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  • Understanding of differential equations and their applications in physics
  • Familiarity with calculus concepts, specifically derivatives and second-order equations
  • Knowledge of mechanics principles related to time evolution
  • Experience with mathematical problem-solving techniques
NEXT STEPS
  • Study methods for eliminating variables in differential equations
  • Learn how to derive second-order differential equations from first-order equations
  • Explore techniques for solving differential equations in physics contexts
  • Review calculus forums for best practices in posting homework questions
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Students in physics and mathematics, particularly those tackling differential equations in mechanics, as well as educators seeking to guide students in proper forum etiquette and problem-solving strategies.

Katy96
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Homework Statement


upload_2015-8-6_16-50-11.png


Homework Equations

The Attempt at a Solution


Any help would be appreciated
 
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katy96:
Please try to post your HW problems in the correct HW forum.

Questions about differential equations should be posted in the Calculus HW forum.

Thanks.
 
SteamKing said:
katy96:
Please try to post your HW problems in the correct HW forum.

Questions about differential equations should be posted in the Calculus HW forum.

Thanks.
It was given in a physics class as part of mechanics assignment
 
Katy96 said:
It was given in a physics class as part of mechanics assignment
It's still a calculus problem so should be posted in the relevant section.

For your question, essentially you want to eliminate every derivative of ##y## and have a DE which just involves ##x## and its time derivatives. Start by differentiating ##\frac{dx}{dt}## to obtain an equation for ##\frac{d^2 x}{dt^2}## which will leave you with 3 equations. You can use these to eliminate ##y## and its derivatives.
 
If this was given as a homework problem, surely you have been given some instruction in solving such problems. There are, in fact, several ways to solve this problem. We have no idea which method would be appropriate for you without knowing what methods you have learned. Part of the problem tells you to "Combine these to form a second order equation for x(t) and find the general solution for x(t)". Do you know how to do that?

Start by differentiating both sides of the given equation that starts "dx/dt= " with repect to t. The result will have a second order derivative of x(t) and a derivative of y(t). Use the other equation to replace that "dy/dt".
 
Or else you can obviously eliminate y between these two eqs. but then you are left with dy/dt in the result. Differentiating first eq. you get dy/dx in terms of x and derivatives and t only which you can then substitute into the other equation you just got.

Not something which requires you to be 'taught' a 'method' IMHO, just a bit of initiative or at most to be told it's possible.
 
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