Recent content by dcppc

Ok, another question when I put in 1/Sqrt[19.66 x-a x^2], I don't know what "0." in that intergral means. Also it has 1. ax and 2. Sqrt[x] what does 0. 1. 2. means?

I thought the intergral of \frac{1}{\sqrt{a x^2}} is \frac{\ln{x}}{\sqrt{a}} Also when I substitute 2b as 59, the integrator gave me an different answer

But the answer contain i, so I don't know it that's correct or not The last time I put in 1/Sqrt[a x^2], it gave me [x log x]/Sqrt[a x^2] Which I don't think is the right answer

Does anyone know how to intergrate \frac{1}{\sqrt{2\beta x-\alpha x^2}} I went to wolfram and type it in, but it gave me a weird number.

--------------------------------------------------------------- Where did your differential equation came from? and actually, I'm assuming that the mass of the Earth is the same all throughout

you guys are right, I thought r=x but that does't mean that x=r, but still, when r approches to 0, the gravity should also gets smaller. Instead I got negative numbers when my r is less than 1

What if the only known value is t=0 and r=0, because since something is going to the center of the earth, then when it's 0 second, the distance it traveled must be 0

but still, ln 0 still is undefined Is there anyway to solve C?

I found out another thing If I plug in 0 for my constant fisrt, then the intergral will be different \int \frac{dr}{\sqrt{\alpha r^{2}}}=\int dt the intergral is \frac{r\log{r}}{\sqrt{\alpha r^2}}+C_{1}=t why is that

I ran into another problem, I was doing a problem similar to this \int \frac{dr}{\sqrt{\alpha r^{2}+C}}=\int dt then \frac{\log{[2\sqrt{\alpha}r+2\sqrt{C+\alpha r^2]}}}{\sqrt{\alpha}}+C_{1}=t and my lst constant is 0 \frac{\log{[4\sqrt{\alpha}r]}}{\sqrt{\alpha}}+C_{1}=t and my r and t...

Thanks guys, it helps a lot

Here is a stupid question How would you solve for \frac{d^2r}{dt^2}=G\frac{M}{r^2} I'm new at this stuff, can anyone tell me?? Assume G and M are constants

I'm trying to find out that if you dig a tunnel through the center of the earth, then how long will it take to get from one end to the other end? I can't use x=1/2at^2+vt because gravity is constantly changing when I approach the center of the earth. And if I find out the gravity, how will I...