HiggsHunter Posted April 26, 2012 Report Share Posted April 26, 2012 A new question, you must be tired by now , : How is the ratio attached obtainable when comparing dplant/dsun- basically everything will be in ratios, what is the math behind the seemingly cross multiplied equation or some such.Secondly, 4 pi cancel out right? Yes, the 4 pi cancel out, the formula is correct and gives the correct numerical result. Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 26, 2012 Report Share Posted April 26, 2012 (edited) 2) Another tiny question is regarding the same wooden blocks. prior information is that the ratio of its displacement at t=1.75 s and t= 0.35 s is 0.76 and thus we are asked to tell what is the ratio of their energies! What can that be?! As it's a 1 mark question it doesn't even expect much working! the correct answer is: 0.57 or 0.58. A graph for this question is attached called ques 2. Thanks in advance!The potential energy of the wave is proportional to the square of the vertical displacement. Since you are given that the ratio of the displacements is 0.76, the ratio of the energies is (0.76)ˆ2 = 0.578. Note that at the times indicated (0.35 s and 1.75 s) the kinetic energy is zero as the water is neither rising nor falling.Yes, only worth 1 mark, I'm afraid! Edited April 26, 2012 by HiggsHunter 1 Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 29, 2012 Report Share Posted April 29, 2012 can someone please remind me when (conditions) linear magnification= angular magnification and why?(equations) please! thank you! Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 29, 2012 Report Share Posted April 29, 2012 (edited) can someone please remind me when (conditions) linear magnification= angular magnification and why?(equations) please! thank you! Linear magnification equals angular magnification when the image is located at the near point, at distance D from the eye. At this point angular magnification = ThetaImage/ThetaObject = (ImageHeight/D)/(ObjectHeight/D) = ImageHeight/ObjectHeight = linear magnification. (Assuming Theta = tan Theta) Edited April 29, 2012 by HiggsHunter 2 Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 29, 2012 Report Share Posted April 29, 2012 Damn! youre students must love you haha! thank you, will rep from pc! Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 29, 2012 Report Share Posted April 29, 2012 Damn! youre students must love you haha! thank you, will rep from pc!Thanks, DropBoite. The only reason that CERN summer students loved me is that I said that it's OK for them to go off and have fun in the mountains instead of working.(As long as they completed their projects on time!) Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 29, 2012 Report Share Posted April 29, 2012 (edited) Damn! youre students must love you haha! thank you, will rep from pc! Thanks, DropBoite. The only reason that CERN summer students loved me is that I said that it's OK for them to go off and have fun in the mountains instead of working. (As long as they completed their projects on time!) ahah! which mountains?! The alps? Hey so I'm also doing mechanics and this question puzzles me: A man works against friction of 470N by exerting a force of 520N on a ball he's dragging. So, the load is moved a horizontal distance of 2.5km in 1.2 hours, find the work done on the load by the force F, The marking scheme says: W-470x 2500. I fail to understad this equation(can't even call it that!) What is it derived from and what the heck are they doing with it? Also, what is W? isn't that the value we're trying to find out? If so then how can they go about using it? peculiar... Right answer: 1.2 MJ (Micheal Jordans.... ) I keep coming short by x10! Also Higgs, Is it possible that you could give me like a few notes to follow on vector addition and subtraction? it really evades me!? perhaps some examples, more of a visual learner, and on the same note circular motion vectors I just don't get! No I don't have any queries, but I'd like to know how to solve these in general. If you remember I'd posted a vector diagram that was the subtraction of momentums and asked about how the direction of the joining arrow mattered? Well, that kind of stuff I really don't get, please help I need a 7 in physics or i'm not getting into Edinburgh! Thank you! Edited April 29, 2012 by DropBoite Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 29, 2012 Report Share Posted April 29, 2012 Yes, the Swiss Alps!It sounds like "=" must be misprinted as "-" in the marking scheme. (The work done W = 470 x 2500 J = 1.175 MJ) Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 29, 2012 Report Share Posted April 29, 2012 Ah! I love those, the looked like chocolate ice cream with vanilla topping when I flew over them last winter. Also could you re-read the previous post? I edited it. Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 29, 2012 Report Share Posted April 29, 2012 (edited) Ah! I love those, the looked like chocolate ice cream with vanilla topping when I flew over them last winter. Also could you re-read the previous post? I edited it. Yes, there is still some vanilla topping on the Dents du Midi. Attached is a view from my house. There is a Maths SL document on vector basics in the Files section here: http://www.ibsurviva...le/735-vectors/ (my member group doesn't have access to that) What course have you applied for, and at which of the Edinburgh universities? Edited April 29, 2012 by HiggsHunter Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 29, 2012 Report Share Posted April 29, 2012 OMFG! the beauty....... gosh, i dont know where you live but that place is on my bucket list! ive never seen them like this before?hqve you considwred selling that picture? ! ill ask the mods about the file, thank you! Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 29, 2012 Report Share Posted April 29, 2012 Yes, this is a pretty spot on the Swiss Riviera towards the east end of Lake Geneva. If you search for "vectors" on YouTube you will find several excellent tutorials. Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 30, 2012 Report Share Posted April 30, 2012 Hey Higgs! I've sprouted yet another question: 'Show the impulse given to the ball by the wall is 0.313 Ns Data: Velocity before collision: 2.2 ms Velocity after: 1.97 mass= 0.075 kg The calculation done is J(impulse) = m x v-precollision+ m x v-post collision. Any explantaion for this calculation would be appreciated. Why are there two impulses? Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 30, 2012 Report Share Posted April 30, 2012 Hey Higgs! I've sprouted yet another question: 'Show the impulse given to the ball by the wall is 0.313 Ns Data: Velocity before collision: 2.2 ms Velocity after: 1.97 mass= 0.075 kg The calculation done is J(impulse) = m x v-precollision+ m x v-post collision. Any explantaion for this calculation would be appreciated. Why are there two impulses? There is just one impulse on the ball when it rebounds from a wall but it is equal to the change in the momentum.Momentum before impact = m x v-precollsion Momentum after impact = m x v-postcollision So impulse = (0.075 x 2.2) - (0.075 x -1.97) = 0.313 Ns Note that while momentum has been conserved, kinetic energy has not, indicating that the collision was inelastic. 1 Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 30, 2012 Report Share Posted April 30, 2012 (edited) Seeing as you got the right answer by subtraction this is yet another marking scheme error...the incompetence is really annoying... Thank you, I repped you. Oh and that vectors file wasn't very helpful at all it was all mathematical stuff. I'm really not good at maths Well I'll continue looking for some helpful material, but I'd be glad if you could offer something! A new question is : What are the various equations or rather the basic equations(not their derived equations) for the three laws of newton and do list any derived ones if you feel they're important, for example I'm not good at calculating friction and resistive force basically, so something there would help! Edited April 30, 2012 by DropBoite Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 30, 2012 Report Share Posted April 30, 2012 Seeing as you got the right answer by subtraction this is yet another marking scheme error...the incompetence is really annoying... The change in the momentum is the difference between the momentum before the collision and the momentun after the collision. But as the direction of the ball is reversed by the collision the new momentum is negative, so it's quite correct to add the numerical values. Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 30, 2012 Report Share Posted April 30, 2012 Oh and that vectors file wasn't very helpful at all it was all mathematical stuff. I'm really not good at maths Well I'll continue looking for some helpful material, but I'd be glad if you could offer something! Did you look on YouTube? Although I didn't watch the videos all the way through, I saw that there were several elementary tutorials on vectors there. Reply Link to post Share on other sites More sharing options...
HiggsHunter Posted April 30, 2012 Report Share Posted April 30, 2012 A new question is : What are the various equations or rather the basic equations(not their derived equations) for the three laws of newton and do list any derived ones if you feel they're important, for example I'm not good at calculating friction and resistive force basically, so something there would help!The equations that you need (including Impulse = m x delta v) are listed on Page 6 of the Physics Data Booklet, which you can take into the exam with you! Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 30, 2012 Report Share Posted April 30, 2012 Erm... how on earth is it sensible to calculate the initial acceleration on a body from the resistive force acting on it!? Ridiculous! Reply Link to post Share on other sites More sharing options...
DropBoite Posted April 30, 2012 Report Share Posted April 30, 2012 A new question is : What are the various equations or rather the basic equations(not their derived equations) for the three laws of newton and do list any derived ones if you feel they're important, for example I'm not good at calculating friction and resistive force basically, so something there would help! The equations that you need (including Impulse = m x delta v) are listed on Page 6 of the Physics Data Booklet, which you can take into the exam with you! Ahaha! I know that, I'm not a fool! But on a serious note, it doesn't seem enough to use those, these IB people are twisted as are their equations... >.> Reply Link to post Share on other sites More sharing options...
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