Integration/Proving help And check my work please

AI Thread Summary
The discussion revolves around deriving specific integral forms for a particle's energy in a central conservative field. For negative energy (E < 0), the goal is to show that the time difference can be expressed as an integral involving real numbers alpha and a. Similarly, for positive energy (E > 0), the expression should involve real numbers beta and b. The user has already demonstrated the case for E = 0 and is seeking confirmation on their integration steps and the overall approach to achieve the desired forms. The focus is on correctly factoring and rearranging terms in the integrals to match the specified equations.
Odyssey
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Greetings,

I am given the following equation.
t-t_{0}=\int_{R_{0}}^{R(t)}\frac{du}{\sqrt{2mEL^{-2}u^4-u^2-2mL^{-2}u^4V(u)}}

This is the total energy of a prticle moving in a central conservative field. m = mass, E = energy, L = angular momentum. The force the particle experiences is F = -Hmu^-3, where H is some constant, m is the mass of the particle, and u the distance. V(u), the potential, is just the negative integral of the force, and it is

-Hm/2u^2

How can I show that the energy, E, if E < 0, then

\alpha(t-t_{0})=\int_{R_{0}}^{R(\Theta)}\frac{du}{u\sqrt{a^2-u^2}}

, for real numbers alpha and a.

And similarly, for E > 0, how can I show it's

\beta(t-t_{0})=\int_{R_{0}}^{R(\Theta)}\frac{du}{u\sqrt{u^2+b}}

, for some real numbers beta and b?

I really need help on this! :confused:

I did show, for the E = 0 case, how it should be done. Please take the time check my work for this part.

Since E = 0, the total energy equation simplifies to:

t-t_{0}=\int_{R_{0}}^{R(\Theta)}\frac{du}{\sqrt{-u^2-2mL^{-2}u^4V(u)}}

then, plugging in V(u),

t-t_{0}=\int_{R_{0}}^{R(\Theta)}\frac{du}{\sqrt{-u^2+m^2L^{-2}Hu^2}}

Let s = m^2L^{-2}H

t-t_{0}=\int_{R_{0}}^{R(\Theta)}\frac{du}{\sqrt{-u^2+su^2}}

t-t_{0}=\int_{R_{0}}^{R(\Theta)}\frac{du}{u\sqrt{-1+s}}

t-t_{0}=\int_{R_{0}}^{R(\Theta)}\frac{du}{u\sqrt{-1+s}}

Since s is only a bunch of constants, we can factor it out.

t-t_{0}=\frac{1}{\sqrt{-1+s}}\int_{R_{0}}^{R(t)}\frac{du}{u}

\ln {R_{\Theta}/R_{0}} = \sqrt{s-1)

then solve for R (\Theta)
R (\Theta) = R_{0}e^{(\Theta-\Theta_{0})\sqrt{s-1}}
 
Last edited:
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