(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

(b) If an object of 0.1 Solar masses fell into the Sun (starting at rest at infinity) calculate what its final speed and energy would be.

Mass of the Sun = 1.99 x [tex]10^{30} kg [/tex]

Radius of the Sun = 6.96 x [tex]10^8 m [/tex]

3. The attempt at a solution

Having done the rest of the question (parts a, c and d), I returned to this part but am having trouble. A couple of years ago we studied free-fall time, but in this question we really aren't given much data. If I had the time, I could backwards-engineer the free fall time to get the velocity, but we don't. Having looked through my notes, I found the free fall velocity:

[tex]v_{ff} = (\frac{2GM}{R})^\frac{1}{2}[/tex]

We thought that integration may be the way to go, but we wouldn't know what with respect to - if we did it to r, then we could put in infinity and zero, but that goes a bit weird. I believe that the R in that equation should be the radius of the object, that we don't know! Also, we want to find the velocity, so changing it to [tex]\frac{dr}{dt}[/tex] won't actually help us. Anyone know where we'd begin?

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# Homework Help: Falling into the Sun

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