Recent content by johngatlin

Stupid book. Thanks.

No, I think the radius of the sun is {7E^8} kilometers. Or at least, that's what the book says.

Yeah. 1 revolution in 1.4 milliseconds...

I find it hard to stomach sometimes when I realize that numerous others have done everything I seem to think, say, or do. In short, I believe I think in clichés. I’ll write something about ethics or how everything’s relative or whatever and then a couple of weeks later I’ll go and read someone’s...

Brilliant. r_{1}^{2}\omega_{1} = r_{2}^{2}\omega_{2} r_{1}^{2}2\pi\frac{1}{t_1} = r_{2}^{2}2\pi\frac{1}{t_2} cancel out: 2\pi \frac{r_{1}^{2}}{t_1} = \frac{r_{2}^{2}}{t_2} cross multiply: t_{2} = \frac{{15^2}{26}}{{7E^8}^{2}} t_{2} = {1.194}{E}^{-14} days. Thanks!

I thought it was r_{1}^{2}\omega_{1} = r_{2}^{2}\omega_{2}

\omega = \omega_o + \alphat \theta = \frac{1}{2}(\omega_o + \omega)t \omega^2 = \omega_o^2 + 2\alpha\theta and others... ?

sorry about the latex. it's really not coming out correctly

The evolution of a star depends on its size. If a star is sufficiently large, the gravity forces holding it together may be large enough to collapse it into a very dense object composed mostly of neutrons. The density of such a neutron star is about 10^14 times that of the earth. Suppose that a...

Thank you.

A disc is mounted with its axis vertical. It has radius R and mass M. It is initially at rest. A bullet of mass m and velocity v is fired horizontally and tangential to the disc. It lodges in the perimeter of the disk. What angular velocity will the disc acquire? So, Angular Momentum is...

I've got it! I still solved for a number on the left side (2.72256) and used your correction on the right: 2.72256 = \frac{7}{5}v_2^2 multiplied both sides by \frac{5}{7} 1.94469 = v_2^2 v_2 = 1.39 Voila!

Ah! My algebra is horrible. Also, I just solved for the initial angular velocity and plugged it in (40 rad/s) on the left. But still, thank you.

using \tau = I \alpha. I mean, we're not told if it's frictionless or not, but if we assume there is, we can use this equation to find it and plug it into F=ma and solve for a. ? The book gives the answer 1.38 m/s I've got to go eat dinner. I'll be back.

You have a sphere of radius .012m and mass .036kg rolling down a slope with an initial speed of .48 m/s. How fast will it be moving after it has dropped 12 cm in elevation? Conservation of energy (taking into account the total KE of a rolling sphere) (w=angular velocity): \frac{1/2}Iw_1^2 +...