quickQuiz #4 (physics)
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21 Nov 2007, 19:54
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Journals
A chain of mass M and length L is suspended vertically with it's lower end touching a scale. The chain is released and falls onto the scale. What is the reading of the scale when a length x of the chain has fallen? Neglect the size of the individual links.
For non-english speakers:
scale - that thing you sit on, and it tells you your weight
Hint:
When the chain falls, do not consider it as an elastic impact. Take it as a plastic impact, i.e. the momentum of the falling piece after the impact is zero.
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Ppuuu, where are youuu?!?
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P.S. Watch http://www.gamestv.org/war.php?wid=3543 tonight!
For non-english speakers:
scale - that thing you sit on, and it tells you your weight
Hint:
When the chain falls, do not consider it as an elastic impact. Take it as a plastic impact, i.e. the momentum of the falling piece after the impact is zero.
-------
Ppuuu, where are youuu?!?
====
P.S. Watch http://www.gamestv.org/war.php?wid=3543 tonight!
coz' i finished high-school a while back ;)
edit : countrys dont even have the same notation sometimes : [
so if you don't like em.. just don't solve em..
<enter random bullshit here and watch quad go horny>
A large birthday cake was baked to celebrate the 6th birthday of Mimi. It was a round cake, made of two layers of vanilla cake; each layer was 18 inches in diameter and 3.5 inches tall. Between the two layers was a quarter inch of chocolate frosting. And covering the top and side of the cake was 3/8" of buttercream frosting.
If the vanilla cake has 140 calories per cubic inch, and the chocolate frosting has 320 calories per cubic inch, and the buttercream frosting has 470 calories per cubic inch, how many 800-calorie servings are in the cake? Please round down to the nearest serving.
Normally mass is descripted by a formula: M = V*d but we can take V as f*L where f = transversive field of the chain(treating it as a rope now, i don't think that's a problem), L = lenght .
M=f*L*d now and f and d are constans cause we are messing with the same chain all the time.
So you count how many times the first mass is bigger than the seeked one:
M/Mx = f*L*d/f*x*d = L/x, where Mx is the mass we seek now.
Mx=M*x/L
[Mx] = kg*m/m = kg
If there is something wrong plz correct me.
if you meant Mx as mass quantified by x you are wrong - it would be M*x. Mx is just M with x in index(just a sign of the mass we are looking for in this task)
x is in metres
L is in metres
M is in kilograms
SO
[N] = kg QUANTIFIED BY m DIVIDED BY m = kg
Secondly, answers please!
It was: Solve for x.
2^(x^2) - (x^2+5x+299) * log_5(|x|) = 0
Now I had no chance of solving it, and I practically gave up, but I ended up after school in a revision session where I brought it up.
The logarithmic rule of:
log_n(a) = log_10(a) / log_10(n) came up, but we weren't sure if that actually gets it anywhere :P
2^(x^2) = [log(|x|) / log(5)] * (x^2+5x+299) <-- is that anywhere near the right way? or...
log_x(5^2^x^2) = x^2 + 5x + 299 ?? o.O
we're way off aren't we?
Anyway....
What's the answer? How is it solved? and Where is it used? :P
2^(x^2) = [log(|x|) / log(5)] * (x^2+5x+299)
The log can be in any base you want:
Log_x(y) = Log_b(x) / Log_b(y)
Usually, the most used logarithm is of base e = 2.718281828... But base 10 is okay as well...
This one is best solved numerically.
Try reading these links for ideas:
http://en.wikipedia.org/wiki/Root_finding
http://en.wikipedia.org/wiki/Bisection_method
Either you start entering numbers in your calculator, or you write a program in C, Pascal, PHP, JavaScript, or whatever you know best to implement that algorithm (that's why i said maths or PC)
Uni of Sheffield.. depends on what you want to do.. It's pretty good in electronics (A+ teaching and research, was their rating last year), nice city (kinda quiet, i like that). What course are you thinking about?
what's the answer out of curiosity, and is it actually used for anything in particular?
And I'm still totally unsure what I want to take. Thinking about something on the lines of Physics/Maths/Engineering but I'm not committed to any field yet. Leaning towards physics.
Oh btw... Are you native to England or did you move there?
Physics... nice, I'm good with physics, but you should really like it if you want to do something useful with it. Otherwise I'd suggest go towards engineering, you can use it more readily do do something in your life. Well.. I might be somewhat biased here, because I did *a lot* of physics in highschool, i still love it, but i got somewhat bored of it, pure theory.
No, I'm not british. I've came to britain just before my first year of university, that is 1 and a half years ago. I'm from Romania.