# Search results

1. ### I Question about Accumulation points

Say D⊂ℝ. Then a ∈ ℝ is called accumulation point of D, when there is a sequence (an) in D "without" {a} and an→a (→ means goes towards) thats how the prof defined it
2. ### I Question about Accumulation points

So we just recently did accumulation points in my maths class for chemists. I understood everything that was taught but ever since I was trying to find a reasonable explanation if the sequence an = (-1)n has 2 accumulation points (-1,1) or if it doesnt have any at all. I mean it's clear that its...
3. ### Determining graphical set of solutions for complex numbers

Ok thx guys I managed to solve it!
4. ### Determining graphical set of solutions for complex numbers

Ok that made things a little clearer...but i still can't figure out how |z+i| could look....
5. ### Determining graphical set of solutions for complex numbers

yeah I know geogebra and I use it quite often, but I haven't been able to figure out how I can view complex numbers...
6. ### Determining graphical set of solutions for complex numbers

Homework Statement So we have been doing complex numbers for about 2 weeks and there is this one equation I just can't solve. It's about showing the set of solutions in graphical form (on "coordinate" system with the imaginary and the real axis). So here is the equation: Homework Equations...
7. ### Determining graphical set of solutions for complex numbers

Hey there! I just have a quick question regarding the graphical adaptation of the solution for the following complex "equation": |(z+i)/z| < 1 What is the solution for this and how do I convert it into an image (with the imaginary and the reality-axis) Thank you!
8. ### Elastic/Inelastic collision upon Traincrash

I thin they are more considered like "monkey see, monkey do" which is maddening. The blue block formula comes from the elastic equation ( where no KE is lost) (combined of momentum conservation and energy conservation)
9. ### Elastic/Inelastic collision upon Traincrash

Yeah well I get it ;) I am just gonna solve it my way and then blame the professor or his students who made these examples... And you have to consider that I have to translate the whole thing from German to English Thx guys, really appreciate your help:kiss::biggrin:
10. ### Elastic/Inelastic collision upon Traincrash

yeah probably :biggrin::DD
11. ### Elastic/Inelastic collision upon Traincrash

Ok, I just gotta make a statement: I am not actually bad at physics, but some of the problems to me pose further problems on how to solve the question, just as you said, the incompleteness of the questions shows that they are not thought out well in my eyes. The example before this on my...

:DD:DD:DD
13. ### Elastic/Inelastic collision upon Traincrash

Yeah for c) they are loosely coupled, so we have inelastic collsions between all pairs. But how will the velocity change there? and for a) and b), I assume, regarding other examples we got for exercise, that they would have mentioned it if the first waggon would "stick" to the other 10 so that...
14. ### Elastic/Inelastic collision upon Traincrash

and for c) it's not a connector socket (sry for my bad english), it's a coupler that goes between trains
15. ### Elastic/Inelastic collision upon Traincrash

Ok so could you explain a little further why b) is wrong? would the formula: v1' = ((m1-m2)/(m1+m2)*v1 be correct for the one waggon? and v2'= (2*m1/(m1+m2))*v1 for the rest of the waggons be correct? to c) well I thought of it like this: The first waggon hits in an elastic collision waggon...
16. ### Elastic/Inelastic collision upon Traincrash

Homework Statement A railway waggon of mass m=20t is travelling with v=18km/h. It then hits 10 other stationary railway waggons, with each one having the same mass of m=20t . (Friction is not being considered) Homework Equations a) Assume the 10 railway waggons are connected through strong...
17. ### Superman's skid marks?

Sry, since I solved the problem over energy I didn't really bother coming back. For those who wondered: Yeah I used g = 10 ms^-2 This thread can now be closed! (can I close it) Thank you everybody for helping me out!
18. ### Superman's skid marks?

Well in the text it says that we should not consider any inelastic collision energy...it sounds strange I know, but it's simplified
19. ### Superman's skid marks?

No, it says that Superman is standing there and "waiting" for the truck and then stopping it. (although that would't work because the truck would be totally smashed, but it's physics for not physics students :P)
20. ### Superman's skid marks?

Holy moly, I think I messed something up big time o0) ok it should be s = 24099m But is the assumption correct?
21. ### Superman's skid marks?

I have to say that Superman is just standing there and not applying any extra force. Ok, and what if I consider an approach over the energies of the two bodies, like this: E(truck) = 1/2 * m(truck)* v^2(truck) and E(superman) = F(braking)* s where F(braking) = m*g*µ and s = braking...
22. ### Superman's skid marks?

I am sorry that the symbol for the friction factor has been bleached away... Ok so you are saying that I could firstly find out what the acceleration a (or in this case the deceleration) is and then insert that into the SUVAT equation to find s?
23. ### Superman's skid marks?

OK, first of all let me thank you for your fast reply, and secondly: Yeah superman stands in front of the truck and is skids over the road. Is my formula still correct or how do I approach it correctly if not? (Probably not as I assumed because there are two masses... but could one say, that...
24. ### Superman's skid marks?

Homework Statement So here is the Problem: A big truck (m=50t) is going at 100km/h. Now the truck can't brake anymore and Superman comes to aid. He (has a mass of m=100kg) tries to stop the truck while he is wearing shoes with a rubber-texture and a friction coefficient of µ = 0.8. Assume that...