# Search results

1. ### Velocity of wind based on the shape of a smoke trail

Hi everyone. My high-school student got the following homework exercise at school which I have problem with: Smoke from the steam locomotive is carried by horizontally blowing wind. Shape of the smoke trail is shown in the attached figure. Using the drawing, determine velocity of the wind...
2. ### B Heating up water versus water with an iron brick

Hi guys, girls, and non-binaries. I'm a private high school teacher and I'm preparing myself to prepare others for polish physics olimpiad. So I delved into books which have a lot of tricky questions and from time to time I stumble upon one I have trouble with. And that's exactly what happened...
3. ### Discrete K-G eq. solutions - problem with integral

I'm reading Klaubers QFT book and I stuck with his derivation of Hamiltonian of scalar field on page 53. To derive it one needs to deal with integrals like this: $$\int\dot{\phi}\dot{\phi}^\dagger d^3x$$ He is using discrete plane-wave solutions and after plugging them in, we end up with...
4. ### Steepest-descent approximation

Hello everyone, my first post :shy: I'm reading Zee's 'QFT in a Nutshell' and I came to one thing that bothers me - he's short discussion of steepest-descent approximation. I've known this thing for quite a long time now, but I've never seen the approximation of the corrections. Here is what...