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  1. O

    Static frictions and moving boxes on top of a box

    ohh I didn't include that. Thanks, it makes sense!
  2. O

    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?
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    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. O

    Calculate wavelength of electron

    Thanks. So in addition to time dilation and length contraction, is this what you call momentum dilation?
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    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
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    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. O

    Conservation of energy and electrons in electric field?

    sweet thanks a lot. what a tricky question
  8. O

    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. O

    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. O

    Monochromatic light and reflection

    so perhaps the index of refraction does not matter?
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    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. O

    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. O

    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. O

    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. O

    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?
  16. O

    LRC circuit:what is the voltage of the capacitor when the generator is at maximum vol

    ohhh nvm from looking at the figure I realized how to do it. By using the triangle at the bottom!
  17. O

    LRC circuit:what is the voltage of the capacitor when the generator is at maximum vol

    a little typo is that I wrote V(R) twice in the diagram. The top one is V(L)
  18. O

    LRC circuit:what is the voltage of the capacitor when the generator is at maximum vol

    Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/cdd8b2f4-1c0d-43ba-8722-fb8b811c5585 Homework Equations V=IR V(C)=X(C)*R The Attempt at a Solution I'm having trouble with number two. I tried finding Z from the frequency and then calculating the...
  19. O

    In what direction does the sphere move between two positive charges

    Homework Statement http://www.screencast.com/users/trinhn812/folders/Jing/media/8fe997e1-46e5-4033-a246-fbad0acb7162 Homework Equations The Attempt at a Solution I understand that in question 25, the conductor becomes polarized and its negative charges will be more attracted...
  20. O

    Korkhoff's loop rule

    http://www.screencast.com/users/trinhn812/folders/Jing/media/3bedaa97-7020-4c5b-85d8-213de24b30a5 For the above problem. A helpful yahoo user told me that I can prove the answer for the above question by solving the problem. He said: Total current is 9/6.2 = 1.45 amps. that all flows thru the...
  21. O

    RC circuit and kirchoff's loop rule

    http://www.screencast.com/users/trinhn812/folders/Jing/media/de5edaba-e848-47f5-82b9-bd770b216e95 I need help with Question 27 specifically. The correct answer is A, but I don't understand why. I thought it would be B according to Korkoff's Loop rule of the inner left loop, where current...
  22. O

    Why would voltage stay the same when a dielectric is introduced?

    http://www.screencast.com/users/trinhn812/folders/Jing/media/9527c4fa-05b4-4baa-98ee-2a3ad47e7e5a I need an explanation for question 6. Why would voltage stay the same across capacitor 3? The dielectric increases capacitance which is inversely related to voltage correct? The equation...
  23. O

    Center of mass: What would make the truck tipover?

    hmm I don't quite understand. would the equation be x*3/120000=2.5? This would mean that the distance of the weight of the load would be ignored.
  24. O

    Center of mass: What would make the truck tipover?

    Homework Statement http://screencast.com/t/ZTk3NDUxNjU I need help with understanding number 18. Homework Equations Center of mase formula: m1x1+m2x2/(all masses) The Attempt at a Solution How do you tell if adding the weight will make the truck tipover. I calculated that...
  25. O

    Multi Tube and fluid pressure

    Homework Statement Now two fluids are placed in the same tube (d). Both sides are open to the atmosphere without pistons. One fluid is water and the other (on top of the water in the left branch of the tube) is an oil of unknown density. l = 135mm and d = 12.3mm. What is the density of the...
  26. O

    How to calculate impulse when velocity is angled?

    Homework Statement Compare impulse for the two objects http://www.screencast.com/users/trinhn812/folders/Jing/media/ecf05e80-8fa7-435c-bfa0-891cf13b176a Homework Equations Change in impulse equation The Attempt at a Solution When you calculate impulse do you have to find the...
  27. O

    Conservation of energy in elastic collision

    Homework Statement http://www.screencast.com/users/ntrinh3/folders/Jing/media/a4165a56-de0d-4a4a-a01e-49242fd505c4 Need help with question 13 Homework Equations Conservation of energy and momentum occurs in elastic collision The Attempt at a Solution Why would the block 2 have an...
  28. O

    How do you calculate Center of mass

    oh so that's it. How about if they just give you the x-coordinate in a system? exe: http://www.screencast.com/users/ntrinh3/folders/Jing/media/010db89d-7781-4262-aa79-57eaf706730f do you just add all of the x-coordinates and divide by how many points?
  29. O

    How do you calculate Center of mass

    Homework Statement I'm confused about how to find the center of mass http://www.screencast.com/users/ntrinh3/folders/Jing/media/a9773d23-38f1-4d28-a6f8-3b681d42d4c2 and http://www.screencast.com/users/ntrinh3/folders/Jing/media/bfb40c40-0068-41e8-ac83-2146e1df3330 Homework...
  30. O

    Calculating velocity of a block on a slope using work theorem

    oh nvm. I stepped away from this problem and realized the angle between the work and force was wrong.
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