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seen Jan 21 '13 at 21:07

Mar
4
awarded  Popular Question
Aug
20
awarded  Popular Question
Jan
17
accepted Why is the spring constant $W_p''(0)$?
Jan
16
asked Why is the spring constant $W_p''(0)$?
Sep
15
accepted Force to use in harmonic oscillation through the inside of a planet
Sep
15
comment Force to use in harmonic oscillation through the inside of a planet
@ChrisWhite I know. I want to understand the concepts. If I was happy with the solution I would have written down what Emilio wrote and been happy with it. I'm not happy until I understand what is happening. The mathematical solution is just a step closer to understanding the concept.
Sep
15
comment Force to use in harmonic oscillation through the inside of a planet
I understand mathematically how you get $M_r = \frac{r^3}{R^3}M_0$, but I can't grasp why this is done. Why is the density of the sphere multiplied by the volume of the planet, and not the volume of the sphere itself?
Sep
15
awarded  Commentator
Sep
15
comment Force to use in harmonic oscillation through the inside of a planet
The first one really was a duplicate. Finding that original question helped me start to visualise the solution I later needed help finishing (in this question). Thank you though.
Sep
15
comment Force to use in harmonic oscillation through the inside of a planet
Wow, this solution gives me exactly the right answer. Thank you. I'm still not sure I grasp what exactly the solution does, but I'm getting there. It's just about mentally visualising it now... :)
Sep
14
asked Force to use in harmonic oscillation through the inside of a planet
Jul
21
awarded  Scholar
Jul
21
accepted How to calculate speed difference between objects close to the speed of light?
Jul
21
accepted How to calculate time dilation in approaching speed of light
Jul
2
awarded  Supporter
Jul
2
comment How to calculate time dilation in approaching speed of light
Thanks to usumdelphini for editing my question - I'm still new to SE and didn't know I could use LaTeX. :)
Jul
1
awarded  Student
Jul
1
comment How to calculate time dilation in approaching speed of light
After an hour of working I realised I did everything right from the beginning, but the online test was unclear as to how the write the answer (ie I wrote 48432 years when I should have written 48000)... I calculated it with t = d/v = 100 000 / 0.9 ; t_0 = t * sqrt(1 - (v^2/c^2)) = t * sqrt(1 - ((0.9c)^2/(c^2)) Thanks a bunch for the help, dmckee!
Jul
1
comment How to calculate time dilation in approaching speed of light
I calculated t_0 to 111 109 years (sounds plausible, traveling 0.9c 100 000 ly). I calculated t = t_0/(sqrt(1 - (0.9c)^2/c^2) but wound up with 254 901 years, which seems really wrong. Shouldn't t < t_0?
Jul
1
comment How to calculate time dilation in approaching speed of light
Ah, I see. So I would calculate how long it would take to travel for example 100 000 ly in 0.9c m/s, ignoring relativity, and use it as t_0 (i.e. what it looks like to the "twin" left on Earth)?