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Homework Statement
A comet is approaching the Sun from a vast distance with velocity V. If the Sun exerted no force on the comet it would continue with uniform velocity V and its distance of closest approach to the Sun would be p. Find the path of the comet and the angle through which it is deflected.
Homework Equations
[itex]\frac{d^{2}u}{d\theta^{2}}+u=\frac{\gamma}{h^{2}}[/itex], where [itex]\gamma=GM[/itex]
[itex]u=\frac{\gamma}{h^{2}}+A\cos{\theta}+B\sin{\theta}[/itex]
Since [itex]\dot{r}=-Vcos{\alpha}≈-V[/itex] where [itex]\alpha[/itex] = the angle between
V and R (R is the distance from the Sun to the comet, green angle in the diagram).
Using [itex]\alpha[/itex]≈0 → [itex]h=RV\sin{\alpha}=pV[/itex]
At t=0, choose [itex]\theta=0[/itex] and u=1/R≈0, du/dθ=-[itex]\dot{r}[/itex]/h=1/p
→[itex]u=\frac{\gamma}{p^{2}V^{2}}-\frac{\gamma}
{p^{2}V^{2}}\cos{\theta}+\frac{1}{p}\sin{\theta}[/itex]
Then u → 0 again, when θ=0, or 2∏-2δ, where [itex]\tan{\delta}=\frac{pV^{2}}{\gamma}
[/itex] Where 2δ is shown below.
and [itex]h=r^{2}\dot{\theta} [/itex] In the usual polar coordinates.
The Attempt at a Solution
What I do not understand is the definition of δ. Especially when it comes to introduction of tanδ ... Can someone explain why we can write tanδ as above ?
I tried to provide as accurate drawing with my paint skills as I could. It was drawn in such a way, the deflected path almost intersected the straight line (almost like a reflection h, where a connect the shortest side with the unique angle of an isosceles triangle )
This example is actually taken from M.Lunn's A First Course in Mechanics, 1991, p33-34.
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