Recent content by Ashiataka

From the wikipedia article Physical Quantity I'm having trouble deciphering the difference here between when roman or italic is appropriate. Any further guidance? Thank you.

One working definition of random is something that can't be predicted. In your case each flip of the coin gives a random result, but over time lots of random results give a clear picture about the nature of the coin.

Yes, of course it is. Thank you.

I'm reading through Douglas Gregory's Classical Mechanics, and at the start of chapter 6 he says that m \vec{v} \cdot \frac{d\vec{v}}{dt} = \frac{d}{dt}\left(\frac12 m \vec{v} \cdot \vec{v}\right), but I'm not sure how to get the right hand side from the left hand side. If someone could point...

I want to calculate the delta V needed to move objects around in a 1-d gravitational field. The relevant equations as far as I can see are the Tsiolkovsky equation, \Delta V = v_{ex} \ln\left(\frac{m_0}{m_1}\right) and the equation for calculating escape velocity. v_e = \sqrt{\frac{2GM}{r}}...

Suppose I have two atoms that independently emit alpha particles. I want to find the mean \Delta T for the events. I then want to extend this for 3, 4 etc. atoms however what I'd like to do for more than 3 atoms is find the smallest delta T for any two emissions. What should I look at to...

Thank you for your assistance :).

Yes, just typos. Corrected as above.

I got this: \nabla \left(\frac{1}{\left| \vec{r}-\vec{r'}\right|}\right) = \frac{ (x^\prime-x) \vec{i} + (y^\prime-y) \vec{j} + (z^\prime-z)\vec{k}} {\sqrt{(x-x^\prime)^2 + (y-y^\prime)^2 + (z-z^\prime)^2}^3} by adding the x, y and z parts of the same form as above.

Thank you. Okay, so doing that I get \frac{\partial}{\partial x}\left(\frac{1}{\left| \vec{r}-\vec{r'}\right|}\right) = \frac{x^{\prime}-x}{\sqrt{(x-x^\prime)^2 + C}^3} by treating x' as a constant.Does that seem along the right path?

Homework Statement Find \nabla\left( \dfrac{1}{\left| \vec{r}-\vec{r'}\right| }\right) Homework Equations The Attempt at a Solution \left| \vec{r}-\vec{r'}\right| =\sqrt{(x-x^\prime)^2 + (y-y^\prime)^2 + (z-z^\prime)^2} and so therefore the derivative of the scalar would be 0. Of...

Suppose I have a picture of a flame, or some other blackish-body like emitter, and I can see that the RGB value of a part of the flame is [106, 216, 177]. How would I go about determining the temperature of this? I'm sure you'd use Wien's law etc, but I can't see how to get from the RGB value...

Thanks Alan. I thought about the unexpected hanging but couldn't quite work out how it applied. Then I looked at Bayes' elegant formulae and got more confused. Anyway, my parcel arrived at 13:45.

I've taken the day off to wait for a parcel at home and (because I'm a physics student and therefore have no ability to actually enjoy my day off) I got thinking about this as a problem. Suppose the delivery company is perfect, i.e. if they say they're going to deliver between 09:00 and 18:00...

Thank you. I've managed to get a very faint green streak on a long exposure. It's quite a lovely effect.