# Search results

1. ### I Decaying Muons on Mt Washington

Dear Experts, Currently I am reading up on Special Relativity. I struggle to understand how from the perspective of the Muon that the distance to the surface of the earth is contracted and thus more Muons arrive at the surface based detector. How can this be? To me the physical space is real...
2. ### Angular Momentum of Glass on a String

Hi Folks, Problem Statement How would one use the conservation of angular momentum to explain the attached picture? The rod is held fixed horizontally..the person holds on to the cork and then lets go...apparently the glass is saved due to this conservation... Relevant Equations Momentum...
3. ### Conservation of Angular Momentum

Ah....I understand.... homework TYPE questions. Ok. I will know in future! Can this thread be moved or shall I repost? Thanks B
4. ### Conservation of Angular Momentum

Hi. I am not a student and this is not homework. I am reading physicsnin my spare time and occasionally I put a question up to get peoples opinions/help. Please advise how I should proceed for future queries.. Thanks B
5. ### Conservation of Angular Momentum

Hi Folks, How would one use the conservation of angular momentum to explain the attached picture? The rod is held fixed horizontally..the person holds on to the cork and then lets go...apparently the glass is saved due to this conservation...
6. ### To stop a moving object -- Momentum or Kinetic Energy

So in laymans terms if I was to describe a situation to my friend about stopping a 18stone rugby player in his tracks by a sufficient tackle..which would be more appropriate...the energy approach? Or perhaps both are equivalent because to stop him covering more distance instantly is equivalent...
7. ### To stop a moving object -- Momentum or Kinetic Energy

How should I look at the problem at stopping a moving object with the following conditions 1) mass m and speed v 2) 0.5 m and 2v 3)0.5m and sqrt 2 v Simple math tells me the number 2 would require more energy to stop it. I can relate to energy better in terms of how to stop a moving mass...
8. ### Automotive Applying torque to a tube

Then under what conditions does this Torque =inertia times alpha hold that one typically sees in textbooks?
9. ### Automotive Applying torque to a tube

Hi Guys, I have a simple annulus of radius 25mm and 15mm of length 50mm where i applieD a torque of T=100000Nmm. Its inertia about its main axis is I=124.9 kgmm2. Therefore i expect the acceleration to be T/I. Its not clear how to confirm this answer in Msc Adams because when i set simulation...
10. ### Interstellar travel

I should choose my words carefully. I meant "propulsion technology" that major firms are investing in etc at the moment.
11. ### Interstellar travel

but assuming we have the technology it would still be impossible to travel through all that dust without damage? To me, that is the ultimate limitation IMHO!
12. ### Interstellar travel

Hi Folks, What is your opinion on this article? It suggest that interstellar travel is a fantasy. http://www.scientificamerican.com/article/interstellar-travel-as-delusional-fantasy-excerpt/# Yet, I read articles about institutions like NASA investing in various conceptual propulsion...

14. ### Black Hole and Information

Hi Folks, Can somenone explain what "information" is with respect to black holes? I thought it was all about mass and energy from both quantum Mechanics and GR perspective. Why does "information" come into it...sounds unusual to say the least. Thanks B
15. ### Relative Velocity of locus of curves

Hi, This is the best I can do regarding a readable picture where I have pasted the relevant eqns. Thanks
16. ### Relative Velocity of locus of curves

Hi. Ok..I will try another picture again tomorrow. I think there should be enough resolution in the photo when you zoom in. Thanks
17. ### Relative Velocity of locus of curves

Hi Folks, I am struggling to see how eqn 4.1.17 is arrived at using using eqn 4.1.10 at bottom of attachment. Its not clear to me what \frac{d \phi}{dt} is...apart from what is given in eqn 2.1.30... Any ideas? Thanks
18. ### Implicit Differentiation

I can say I fully understand but perhaps some one can enlighten me regarding what is involved converting derivatives to differentials....for my own understanding and information
19. ### Unit Normal for Epicycloid

Ok, great thanks. I should work it out now.
20. ### Unit Normal for Epicycloid

Hi Folks, I got stuck towards the end where it ask to derive the unit normal (eqn 3.2.29 I don't know how they arrived at n_x. I have looked at trig identities....and I have assumed the following n_x=\frac{N_x}{|N_x|} I dont see the (r+p) term anywhere in neither the top nor bottom. PS: I...
21. ### Find Lambda from this arbitrary triangle

Hi RUber, I have it. The extended segment of "a" which forms a right angled triangle with P is Pcos(pi-psi). The tan of lambda is obvious. Thank you very much. I have learned a new way of tacking triangles!
22. ### Find Lambda from this arbitrary triangle

Hi, thanks.... This is as far as I got....see attached.....
23. ### Find Lambda from this arbitrary triangle

Folks, I am puzzled how one obtains equation 3.2.31 based on the schematic as attached! Can you help? Is there an online source I can refer to to learn how to obtain angles and magnitudes of complex schematics? Thanks
24. ### Implicit Differentiation

Ah ok, So I add in an extra step wrt to x \phi_x+\phi_y \frac{dy}{dx}=0 *by dx to give \phi_x dx+\phi_y dy=0 or wrt to y \phi_y+\phi_x \frac{dx}{dy}=0 *by dy to give \phi_y dy+\phi_x dx=0
25. ### Implicit Differentiation

Sorry, I understand the derivative of a constant is 0 but I still don't see how you get the last term where you have dx and dy by themselves...even if i try \phi_x dx=-\phi_y dy= \frac{dy}{dx}=-\frac{\phi_x}{\phi_y}
26. ### Implicit Differentiation

Folks, Differentiate implicitly \phi(x,y)=0 I get: wrt to x \phi_x+\phi_y \frac{dy}{dx} and wrt to y \phi_y+\phi_x \frac{dx}{dy} however I dont know how this is derived \phi_x dx+\phi_y dy=0
27. ### Shankar- Simultaneous Diagonalisation of Hermitian Matrices

Folks, What is the idea or physical significance of simultaneous diagonalisation? I cannot think of anything other than playing a role in efficient computation algorithms? Thanks
28. ### QM Sankar 2nd edition -- gram schmidt process on example 1.3.2

I have been studying this further. It is clearer to me now and I now know how to proceed with this problem. Thanks
29. ### Is matrix hermitian and its eigenvectors orthogonal?

OK guys, thank you. I can see how that holds for ##\lambda=1##. Onto my next problem :-)
30. ### Is matrix hermitian and its eigenvectors orthogonal?

Thanks for the video, very useful I have expanded ##det(\Omega - \lambda I) = 0## to get ##\begin{bmatrix}1-\lambda& 3 & 1\\ 0& 2-\lambda&0 \\ 0& 1 &4-\lambda \end{bmatrix}## For ##\lambda=4## say we get the following ##\begin{bmatrix}1-4& 3 & 1\\ 0& 2-4&0 \\ 0& 1 &4-4...