# Recent content by okgo

1. ### Static frictions and moving boxes on top of a box

ohh I didn't include that. Thanks, it makes sense!
2. ### Static frictions and moving boxes on top of a box

hmm so far.. m= mass of box and M=mass of cart. I assume the acceleration of the box and cart is the same. F(box)=force(friction)=umg=ma ug=a F(cart)=force done by you=Ma Substitute ug=a into the equation. u*g*M=Force so mass of the box doesn't matter?
3. ### Static frictions and moving boxes on top of a box

Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/d77fab7d-ece6-4c9c-be65-bf41f94770fd Homework Equations I got the right answers doing the work shown, but I don't understand the logic of how I solved question 4. The Attempt at a Solution
4. ### Calculate wavelength of electron

Thanks. So in addition to time dilation and length contraction, is this what you call momentum dilation?
5. ### Calculate wavelength of electron

Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/9582a1aa-b21a-4e50-8774-b60866a7d666 Homework Equations lambda=h/p The Attempt at a Solution So I got 4.04E-12 m but the book says the answer is 3.23pm I'm not sure where I'm wrong
6. ### How far from the lightbulb can you stand to see it? photon problem

Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/23298f1b-2ef4-4cdf-8b7a-58c9be07335a Homework Equations E=hf The Attempt at a Solution I'm not even sure how to get the distance for this problem.
7. ### Conservation of energy and electrons in electric field?

sweet thanks a lot. what a tricky question
8. ### Conservation of energy and electrons in electric field?

Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/6596c399-feb6-49cf-82a7-d6d16c2a88e8 Question 17 Homework Equations So I solved this problem using kinematics and would like to learn how to solve it use conservation of energy. I can't seem to get the right...
9. ### Monochromatic light and reflection

lol no. This was a practice exam and half the people got it wrong. I guess the teacher was just being tricky.
10. ### Monochromatic light and reflection

so perhaps the index of refraction does not matter?
11. ### Monochromatic light and reflection

http://www.screencast.com/users/trinhn812/folders/Jing/media/07c73e88-45a9-4703-91e1-237b20135d2c I'm not sure why the answer is A. I tried reasoning myself that it has to do with the critical angle, but I can't seem to convince myself.
12. ### Thin hair diffraction

I'm still a bit confused as to why the dot like patterns are horizontal. What is the black dot? Is that suppose to indicate a circular single slit? In the following picture, I'm confused as to how the picture on the left translate to the one on the right. As the diffraction pattern on the left...
13. ### Plagued by Snell's law and geometry

I'm just having a horrendous time trying to figure this problem out. My geometry is really lacking. http://www.screencast.com/users/trinhn812/folders/Jing/media/64c9342a-985a-4bb2-9e29- [Broken] 98b5b5ebb1ad
14. ### Thin hair diffraction

I believe so. The wavelets due to huygen's principle can still propagate at the edges of the hair. Do the wavelets propagate horizontally around the vertical hair? It just confuses because single slit oriented vertically produce vertical patterns. But hair doesn't and I am told it acts similar...
15. ### Thin hair diffraction

So I understand that thin hair or wire can make a diffraction pattern, but why would the diffraction pattern be horizontal when the hair is vertical?