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Find the equations of the trajectories?

  • Thread starter Math10
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  • #1
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Homework Statement


Find the equations of the trajectories of y"+y^3=0.

Homework Equations


None.

The Attempt at a Solution


The Undamped Case:
y"+p(y)=0
v(dv/dy)+p(y)=0
integrate
v^2/2+P(y)=C
---------------------------------
So following the formula above:
The answer I got is v^2/2+y^4/4=C, but the answer in the book says v^2+y^4/4=C. What's wrong?
 

Answers and Replies

  • #2
Simon Bridge
Science Advisor
Homework Helper
17,847
1,644
Did you, blindly, followed a formula?

What makes you think the formula applies in this case?
Did you follow the formula correctly?
Did you check your algebra?
Did you check your arithmetic?

Maybe the book made a typo?
 

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