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YPang
United States4024 Posts
The passengers in a roller coaster car feel 40% heavier than their true weight as the car goes through a dip with a 34 m radius of curvature. What is the car's speed at the bottom of the dip? I don't really even know how to get started on this problem, this is like what i have so far.. I don't think im even pluggin the numbers in correctly... i got so confused on this chapter D:> PS: Double click to enlarge. ![[image loading]](http://img505.imageshack.us/img505/1582/99998949qa4.jpg) ![[image loading]](http://g.imageshack.us/img505/99998949qa4.jpg/1/)   | ||
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BuGzlToOnl
United States5918 Posts
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YPang
United States4024 Posts
On December 09 2008 09:33 BuGzlToOnl wrote: Is w suppose to be your angular momentum? wapp = apparent weight w=weight | ||
micronesia
United States24784 Posts
The passengers in a roller coaster car feel 40% heavier than their true weight This means the normal force exceeds the weight obviously. Specifically, Fn = 1.4 * W as the car goes through a dip with a 34 m radius of curvature. r = 34m and the direction of the centripetal acceleration (and net force) is up What is the car's speed at the bottom of the dip? We need the free body diagram. ^ Fn | | [ ] | | \/ W Newton's Second Law: Fnet = ma + Show Spoiler + Fn-W = m v^2 / r Substitute in Fn = 1.4 W 1.4W - W = mv^2/r W(.4) = mv^2/r .4*mg=mv^2/r 0.4*(9.8) = v^2 / 34 v = 11.54 m/s In my head I hope that's correct XD | ||
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Agro_Z
United States138 Posts
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vAltyR
United States581 Posts
+ Show Spoiler + 40% heavier than normal weight is 1.4*g, where g is the acceleration due to gravity at the earth's surface. centripetal acceleration is determined by the formula a=v^2/r. Therefore, 1.4*g=v^2/r. you know g and r, so it's just a matter of plugging it in and solving. | ||
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micronesia
United States24784 Posts
On December 09 2008 09:41 Agro_Z wrote: Hmm, which physics are you in? I'm in physics B, but in my circular motion chapter, we never had to deal with apparent weight. This sounds bad. Double check an ap physics b review book I suggest. | ||
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Cobalt
United States441 Posts
On December 09 2008 09:49 micronesia wrote: This sounds bad. Double check an ap physics b review book I suggest. My physics class hasn't even gotten past ballistic motion, and mine is the highest physics class my school offers. | ||
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Kentor
United States5784 Posts
N - mg = mv^2/r 1.4mg - mg = mv^2r .4g = v^2/r v=sqrt(.4rg) | ||
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Empyrean
17070 Posts
On December 09 2008 10:21 Cobalt wrote: My physics class hasn't even gotten past ballistic motion, and mine is the highest physics class my school offers. This late in the year? Even for high school level AP Physics courses, kinematics should've been finished by three weeks at the latest. The AP Physics tests aren't exactly cakewalks, either. They're much more difficult than, say, the AP Calculus tests or the Chem/Bio tests (the non-hard science APs such as history, gov, psych, enviro sci etc., are much easier, don't even worry about them). Honestly, AP Physics B is probably the most difficult out of the AP tests, followed by AP Physics C (paradoxically enough). If you're planning on taking the test for any sort of college credit, I would definitely recommend seeing what sort of outside tutoring you could get (at a reasonable price, of course. Try bored college students in the major?) and forming a study group yourself to go over concepts in review books. If not, then just enjoy your physics class. Physics is one of the most interesting things you'll ever learn in school, in my opinion. Also AP Language tests are a bitch if you aren't a native speaker. Oh, and for the next two days I absolutely hate physics because my final is on Wednesday and I haven't started studying ahhhhhhhhh fuck my life. | ||
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micronesia
United States24784 Posts
On December 09 2008 10:47 Empyrean wrote: Honestly, AP Physics B is probably the most difficult out of the AP tests, followed by AP Physics C (paradoxically enough). I've heard a lot of people say this and I emphatically disagree :-/ I found the AP Physics B to be relatively easy relative to the C... I actually didn't take the C but I've since graded them :p | ||
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Empyrean
17070 Posts
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Malongo
Chile3472 Posts
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YPang
United States4024 Posts
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micronesia
United States24784 Posts
On December 09 2008 11:34 Empyrean wrote: Well, what I've found to be the trend (and definitely correct me if I'm wrong, because you obviously have much more experience in this), is that out of the schools that offer both AP Physics B and C, they do a much better job preparing you for the AP C test because of the sheer quantity of material for the AP B test that many students just can't handle. At least that's what it was like at my school and a few others. Hm I guess if you have a strong math background then the ap physics c isn't that bad. I didn't take calculus in high school so I couldn't take ap physics C. I took regular physics a year ahead, and then took AP Physics B so since half of it was repeat... the 'sheer quantity of material' didn't feel so bad to me. | ||
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Pendragon
Canada23 Posts
On December 09 2008 11:36 malongo wrote: micronesia just solved it perfectly, people of the world learn to do free body diagram before posting. ACII free body diagrams aren't cool. | ||
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SpiritoftheTunA
United States20903 Posts
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BuGzlToOnl
United States5918 Posts
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sith
United States2474 Posts
A+ ez. | ||
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emperorchampion
Canada9496 Posts
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