# Forum (English version)

You can use MathJax in the discussion.

### Jungle King 29. 11. 2017, 20:55

https://www.google.co.in/search?client=safari&rls=en&q=rubber+band&ie=UTF-8&oe=UTF-8&gfe_rd=cr&dcr=0&ei=MRAfWqjiAcPy8AewuoSoBg A rubber band is a loop of rubber. So, the force constant used should be 2k, and the answer, $\sqrt{2}$ times the present answer, i.e., 9.8m/s

### Organizers 29. 11. 2017, 21:16

We are sorry the task is not hundred percent unambiguous. The rubber band should be considered as a one object with total stiffness k.

### Carmel CornSUPERSTARs 玉米超級明星 29. 11. 2017, 20:41

Where can we find the solution?

### PMF 29. 11. 2017, 20:36

Solutions, problem 30, it is written that r3 is inner radius, but calculated as it was outter radius??

### Organizers 29. 11. 2017, 20:50

We are sorry. There is an error in translation. There should be written "outer radius" in the task.

### Organizers 29. 11. 2017, 20:08

The next edition of Online Physics Brawl will be held on 28th November 2018.

### Organizers 29. 11. 2017, 20:04

Congratulation to the winners in their respective categories: Vypínači Hejčín (A) Hawkingovo zářená (B) #To je na vás. :]》 (C) SuperPentaPhosphate (Foreign HS) FtáKopySk (Open)

### the CATALYST 29. 11. 2017, 19:52

for q24, which frames are the speeds given in?

### Organizers 29. 11. 2017, 19:57

Consider a static Earth and an observer standing on it.

### Vrli Zeničani 29. 11. 2017, 19:36

mozel neko nesto sapnut

### WWP South 29. 11. 2017, 19:16

For fol 25, over what time period are you saying the average detection is 10?

### Organizers 29. 11. 2017, 19:23

Long enough to get a statistically significant average, but short enough to neglect any supposed decrease of activity of the source.

### The Laplace Army 29. 11. 2017, 18:55

is fol 28 consistent?

### Organizers 29. 11. 2017, 19:00

We believe that our solution is correct (and two teams in the competition have already solved it). If you have some more specific questions, send it to online(at)fyziklani.cz

### Life is Stern and Earnest 29. 11. 2017, 18:20

Oh sorry, could you delete this comment? But get back to us on the question?

### Organizers 29. 11. 2017, 18:22

It has been deleted, send the question via e-mail.

### Life is Stern and Earnest 29. 11. 2017, 18:22

what is the email we should send to?

### Organizers 29. 11. 2017, 18:25

online(at)fyziklani.cz