# Recent content by PEZenfuego

1. ### Determining Spring Constant in Ion Pair

For the units to work out I HAVE to know r0. Maybe my value is crap, but at least my solution shows the understanding is there. It turned out to not be too hard...maybe a little convoluted. Thanks for the help!
2. ### Determining Spring Constant in Ion Pair

So I took r0 to be the ion separation between na and cl which was 0.28 nm. Using this and all of the other information, I ended up with a frequency of 1.19*10^13 hertz. Is this reasonable?
3. ### Determining Spring Constant in Ion Pair

Well, I end up with the spring constant being \frac{k\alpha e^{2} \left(m-1\right)}{r_{0}^{3}} and plugging this into mathematica shows the tangent, which is in good agreement for small deviations. Great...so now what?
4. ### Determining Spring Constant in Ion Pair

Finding the derivative of force will show the points at which it is minimized and maximized, but I all ready know that. What good is it?
5. ### Determining Spring Constant in Ion Pair

I did this! So I converted r to r_{\circ}+\Delta r and get F=-k\alpha \frac{e^{2}}{r_{\circ}+\Delta r}[1-\left(1-\frac{\Delta r}{r_{\circ}}\right)^{1-m}] and say that \frac{\Delta r}{r_{\circ}} is much less than 1 (which is reasonable for small angles). I was hoping that this would get rid of...
6. ### Determining Spring Constant in Ion Pair

Homework Statement The force between an ion pair is given by F=-k\alpha\frac{e^{2}}{r^{2}}[1-\left(\frac{r_{\circ}}{r}\right)^{m-1}] Find the value of r where the equilibrium position is. Determine the effective spring constant for small oscillations from the equilibrium. Using...
7. ### Potential and Thermal Energy

Thanks for looking over it. One concern was that the height doesn't factor into this ratio. That seems a little strange to me, but I can accept it as true. This isn't necessarily a difficult problem, but it was difficult to keep track of the variables as there are essentially three stages to the...
8. ### Potential and Thermal Energy

Now I'm confused again :confused: Okay, step by step. Follow along and tell me where my mistake is. Momentum is conserved. Kinetic energy is not. Step 1: The potential energy of the car an earth turns completely into kinetic energy of the car (ignoring kinetic energy of the earth). Step...
9. ### Potential and Thermal Energy

I got 1/2. Sorry, it is there at the bottom, just not in words.
10. ### Potential and Thermal Energy

That sounds like exactly what I did! So do you think my answer is correct?
11. ### Potential and Thermal Energy

So is it okay to consider the kinetic energy of the first car before and after the collision and the kinetic energy of the second car before and after the collision separately like I did?
12. ### Potential and Thermal Energy

Homework Statement Starting from rest, a railroad car rolls down a hill 20 m high and hits another identical car at rest. The cars lock together after the collision. What fraction of the first car's change in potential energy is converted into thermal energy in the collision? Homework...
13. ### Mathematica [Mathematica] Simple Problem with the plot function

That's really neat and useful. I was so accustomed to just glazing over (1-Sqrt)/2, that I forgot that it was negative. If you raise it to the power of 1/2 for example, then the answer is imaginary. That's why it is not a real-valued function, correct? Thank you, sir.
14. ### Advice and Insight for choosing between Math and Physics

Ouch. I do not claim to be awesome. I have no idea what I am doing here and I need help from people who do (and who are thereby more awesome than I am). My question is where to start. If I had a good idea about what I wanted to ask, then I wouldn't need suggestions. What things do I need to be...
15. ### Advice and Insight for choosing between Math and Physics

Right now I am on track to be a math and physics double major, but I just finished my freshman year, so I haven't declared yet (all male liberal arts college). I won't know my GPA until May 15th and since it is freshman year, it doesn't matter a whole lot. I may have a 4.0 (on a 4 point scale)...