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  1. RabbitWho

    I Odds ratio and percentages... absolute beginner

    The fact that a number can increase in size in this self-referential way is neat. You number people and the things you do.
  2. RabbitWho

    I Odds ratio and percentages... absolute beginner

    Oh wait wait wait.. So the way odds ratio differs from percentage is that it is ALWAYS in reference to something else? Is that it? So 1 is ALWAYS the same as the thing its in reference to, and anything above 1 tells you how much it has changed... So if the GAD odds ratio for people with MD...
  3. RabbitWho

    I Odds ratio and percentages... absolute beginner

    Imagine that the chances in the USA of adult men having GAD are on average 1 in 100. But what of the subset of adult men who already have MD? What are the chances that such men will have GAD as well as MD? An odds ratio tells us about the increase in the chance that such men will have GAD...
  4. RabbitWho

    Finding the force of repulsion between two point charges

    Homework Statement [/B] Find the force of repulsion between two point charges of +1C and +3C if they are placed 1 m apart in a vacuum. On which charge is the greater force? ε=8.9x10-12 π = 3.14 d = 100 cm q1 = 1 q2 = 3 Homework Equations F= 1/4πε0 Q1 Q2/d2 The Attempt at a Solution The...
  5. RabbitWho

    Finding the force of repulsion between two point charges

    cool Ah! Sorry, this was a big mistake. I was looking at the sample method, where they were using microunits This is confusstipating because in the sample the book has an example with 50 cm and uses 50 as d in the sample method, not 0.5.. But ok! cool :) Ah yes thank you. Was confusing...
  6. RabbitWho

    Suggestion Floating menu bar

    I don't have to read the icons so they are the smallest size possible. I don't know how to do that. It was just a suggestion, forget about it. I really don't think the menu has any purpose other than to take up space, if I wanted any of those functions I could scroll up to them. But obviously I...
  7. RabbitWho

    Suggestion Floating menu bar

    I need to be able to see what I a reading, which I can't if I zoom out.
  8. RabbitWho

    Suggestion Floating menu bar

    What is the purpose of that floating menu bar on top, it is quite cumbersome for me on my small screen with its big writing. You know in the 90s there were frames on every website and we got rid of them because they were universally hated. Now that we all have wide-screen computers and...
  9. RabbitWho

    Finding the force of repulsion between two point charges

    Hello! So this is going into physics because it is a physics problem, but it is maths that is the real problem. So if you came here to help someone with physics and not maths I'm sorry. 1. Homework Statement Find the force of repulsion between two point charges of +1C and +3C if they are...
  10. RabbitWho

    B Vocabulary: What do you call spinning on the opposite axis?

    So imagine you have two disks, and from your perspective one is spinning on its vertical axis and the other one is spinning on its horizontal axis. What do you call that? And what would it mean to "spin at the opposite polarity" if such a sentence makes any sense at all? Thank you! Sorry if...
  11. RabbitWho

    Find the mass of a metal block with heat capacity 60JK

    ah I get it! I have to divide a million by 600, and I understand why, too. Thank you! :)
  12. RabbitWho

    Find the mass of a metal block with heat capacity 60JK

    OK so 600JK -1 (600 joules per kilo per Kelvin) is necessary to change the temperature by ` 1 MJ of heat is lost... Is that 1 megajoules ? so that is 1 million joules? The answer at the back says that the change in temperature is 1667 degrees Celsius.. I am sorry I can't see how to get that...
  13. RabbitWho

    Find the mass of a metal block with heat capacity 60JK

    Homework Statement A metal block of heat capacity 60 J K -1 loses 1MJ of heat energy to its surroundings. Find the decrease in its temperature. Homework Equations Q = m c Δ θ Heat energy added = mass x specific heat capacity x rise in temperature heat energy lost = blah blah blah x drop in...
  14. RabbitWho

    Finding the angle of refraction

    Ah! Thank you, that was a silly mistake. Let me see if I can do it now 0.413 = dNa Sin 20 degrees = 0.3420 sin r [sin theta diamond] / 0.3420 = 0.413 I think I am still going wrong somewhere because I can't see how to get 55.9 degrees out of what I have o.O Sorry about this
  15. RabbitWho

    Finding the angle of refraction

    it has to be and, doesn't it? Because all it says is "the refractive index", and the normal one to give is light travelling from air (or a vacuum) into the medium.
  16. RabbitWho

    Finding the angle of refraction

    Sorry about that! I should have realized it wouldn't be clear. we are using n for refractive index as well, but aNd (and) d stands for diamond and a stands for air, so aNd is the refractive index of light travelling from air into a diamond and dNa is the refractive index of light travelling...
  17. RabbitWho

    Finding the angle of refraction

    That formula isn't taught in my book. I saw them explain it on Kahn Academy but I don't really understand it. I think it is just another way to express the same thing. I have to stick with the formula given for my exam. If I use any formula which is not on the syllabus there is a good chance I...
  18. RabbitWho

    Finding the angle of refraction

    Homework Statement The refractive index of diamond is 2.42. A ray of light passing from the inside of a diamond into air makes an angle of incidence of 20 degrees. Find the angle of refraction. Homework Equations n = refractive index aNd = 2.42 (my book said the speed of light in a vacuum and...
  19. RabbitWho

    1/u + 1/v = 1/f

    Saw this a week and a half ago, I liked it, it helped me. Now studying lenses rather than mirrors, forgot what you had said but remembered you had answered so came back here and got helped again. Thank you!
  20. RabbitWho

    Describe your work like you're a 6 year old

    I did this too! Only I also had to bring food to the people as well. This was the worst job I ever had because the people were very unfriendly to me and often angry or rude for things that weren't my fault. This is why I am very very very very nice to the people who bring me food now.
  21. RabbitWho

    Describe your work like you're a 6 year old

    I spend 3 hours a day explaining things to nice people then I go home and read books... Put like that it sounds pretty awesome
  22. RabbitWho

    A (possibly controversial) poll question on marriage

    Depends on the people. Their personalities. Their expectations. Their plans for the future. Their gender. Their circumstances. The culture in which they were raised. Too many variables. Can't be answered.
  23. RabbitWho

    Finding distance of image from mirror given focal length

    Homework Statement An object is at a very large distance from a concave mirror of focal length 40cm. Find the distance from the image to the mirror. Is the image real or virtual? Homework Equations 1/u + 1/v = 1/f The Attempt at a Solution [/B] 1/u + 1/v = 1/40 The image has to be real...
  24. RabbitWho

    Finding apparent depth real depth and refractive index

    Thank you! that makes sense. I got the answer right now :)
  25. RabbitWho

    Finding apparent depth real depth and refractive index

    Homework Statement refractive index = 1.33 (water) real depth = 10m Homework Equations refractive index = real depth divided by apparent depth The Attempt at a Solution I'm going to call apparent depth X 1.33 = 10/x So I multiply 10/x by 10 so that i have x and 1.33 x 10 is 13.3... that's...
  26. RabbitWho

    1/u + 1/v = 1/f

    That is what it seems like, right, but the book says that even if you know from the diagram that the image is virtual you should use the formula for real Here is what it says exactly "An object is placed 12cm in front of a concave mirror of focal length 20cm. Find the position, nature, and...
  27. RabbitWho

    1/u + 1/v = 1/f

    Could I ask a related question? The book gives me a problem where the image is clearly virtual because the object is placed inside the focal length, but it tells me "let us assume we do not know whether the image is real or virtual and use the formula for a real image" Why is this? When I use...
  28. RabbitWho

    1/u + 1/v = 1/f

    I did google :( I have watched about 6 videos on the topic and read about it in two separate textbooks, I know it seems really simple to you but "just google it" hasn't helped, so I came here. Thank you for specifying that it only applies to curved mirros, I'll have to buy one.
  29. RabbitWho

    1/u + 1/v = 1/f

    Homework Statement u= distance from the object to the mirror v = distance from the image to the mirror f = focal length I don't understand what they are talking about and I would like to 2. Homework Equations If the image is real 1/u + 1 v = 1/f If the image is virtual 1/u - 1/v = 1/f The...
  30. RabbitWho

    Expressing measurements in SI units

    Sorry! A van driver cut me off and I fell off my bike trying not to crash into him today so I am studying with a nasty headache. Thank goodness for helmets though, right? Watch out for cyclists, van drivers, we are a squishy and fragile people. 5x109N 9g / 1cm3 can get to 9 x 103 kg m-3 I'd...
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