Sunday

April 20, 2014

April 20, 2014

Total # Posts: 16,179

**math**

It was in a steel box lined with layers and layers of bubble wrap ( one of the many ways my students use in the contest)

**Calculus**

so it is positive for x>.316 and for x <.316

**Calculus**

Note that you did the second derivative correctly. It is easier to write it their way y" = 10e^(-5x^2)(10x^2-1) It is zero at x = +/- .316

**Calculus**

first http://www.wolframalpha.com/input/?i=plot++e^%28-5x^2%29 Then this for second derivative and graph https://www.wolframalpha.com/input/?i=second+derivative+of+e^%28-5x^2%29

**Calculus**

first http://www.wolframalpha.com/input/?i=plot++e^%28-5x^2%29

**Spanish needs Sra**

Well, all I can say is I understand you and can follow the directions just fine, but I am no Spanish grammar expert so hope one comes along.

**physics**

mass 1 accelerates downward at a so mass 2 accelerates up at a tension = T mass 1: m g - T = m a so 3 g - T = 3 a mass 2: T - mg = m a so T = 2 (g+a) substitute T in mass 1 equation 3 g - 2(g+a) = 3 a g - 2 a = 3 a a = g/5 = 9.81/5 = 1.962 You could also use the total mass of ...

**science (check please (:)**

Wow, glad you chose the right answer :)

**science (check please (:)**

DO NOT USE BOTTLED WATER !!! 1. It is a waste of money 2. It fills the ocean with plastic bottle remains. That is once it gets thrown off the boats and bridges. 3. It burns up energy and resources for manufacture of bottles, distribution fuel etc etc anyway your answer is right.

**science (check)**

You are correct, but did you have to ask? :)

**math help**

for 5 days 2/5 + 1/5 + 3/5 = 6/5*5 = 30/5 Sat 3 *4/5 = 12/5 Wed -2/5 for wet Pepper 30/5 + 12/5 - 2/5 = 40/5 = 8 hours

**math**

http://www.jiskha.com/display.cgi?id=1396046268

**science (check)**

Yes, but the individuals may be fish or whatever.

**Math for grade 6 peace**

96 = 0.48 x x = 96/0.48

**Physics**

Take moment about the left end total mass = 20 + 14 + 39 = 73 kg That is force up from pivot (I am going to do force in kilograms because g will cancel everywhere.) pivot distance from left = 1.4 Distance left to 39 kg = x (our L is (x -1.4) ) moments about left end 14 * 0 - 7...

**science**

distance = speed * time same time, higher speed --> bigger distance

**Math**

x + 15 + 2x + 27 = 180 3 x = 138 x = 46

**math help!!**

[ (x^2+5x) - 6 ] [(x^2+5x) + 6 ] (x^2 + 5 x - 6) (x^2 + 5x + 6) now if the back of your book says (x^2 + 5 x + 6)( x^2 + 5 x - 6) That is the SAME

**math help!!**

You got the second one, just reversed x y = y x !

**geometry**

width of alley = 60 tan 40 so second building = 60 + 60 tan^2 40 =60 (1 + tan^2 40) = 110 ft

**geometry**

ratio of ANY lengths in similar figures is the same 12/16 = 3/4 2. Ratios of ANY areas is length ratio squared 9/16 3. 54 * 16/9 = 96

**math help**

That is exactly what we got x y = y x the order is just reversed

**math help**

LOL, no need for wolfram !

**math help**

remember - -d = + d

**math help**

[ (a-b) - (c-d) ] - [ (a-b) + (c-d) ] [ a - b - c + d ] [ a - b + c - d ]

**Calculus Help Please!!!**

One of us made an arithmetic mistake. It is up to Tanya to get it right :)

**Calculus Help Please!!!**

rate of change of temp proportional to temp above room temp which is 20 to make it easy on the arithmetic define T' = real T - 20 dT'/dt = k (T') dT/T' = k dt ln T' = k t T' = C e^kt let's call t = 0 at 1:30 T = 32.5 so T' = 12.5 12.5 = C e^0 = ...

**Calculus Help Please!!!**

I am going to assume it is algebra first take t = 0 at 1:30 T = Ti - k t Ti = 32.5 so T = 32.5 - k t 30.3 = 32.5 - k (1 hour) k = 2.2 so T = 32.5 - 2.2 t 37 = 32.5 - 2.2 t t = - 2.04 call it 2 hours so by that linear model 11:30 am now I will work on the more realistic calculu...

**Calculus Help Please!!!**

Are you sure this is calculus? You want exponential decay to room temp? Or is it algebra and you want a linear function?

**math**

Yes !!! You got it. even the -1 * -1 = + 1 part

**math**

sorry about the caps, was doing tax returns with caps lock on

**math**

yOU HAVE [X - [Y-Z) ] THAT IS [ X - Y - NEGATIVE Z ] - A NEGATIVE IS POSITIVE [ X -Y PLUS Z ]

**math**

x^2-(y - z)^2 exactly the same way let a = x let b = y-z now you have a^2-b^2 = (a-b)(a+b) so [x -(y-z) ] [ x + (y-z) ] (x-y+z)(x+y-z) you were close

**math**

let x = (a-b) let y = c then you have x^2 - y^2 = (x-y)(x+y) now put in (a-b) for x and put in c for y

**physics**

the only one that lacks serious damping is the light in a vacuum.

**Chemistry URGENT**

I see nothing wrong with them.

**Chemistry URGENT**

Oh, divide by 2 C6 H10 O5 + 6 O2 ---> 6CO2 + 5 H2O

**Chemistry URGENT**

C6 H10 O5 + O2 ---> CO2 + H2O we need an even number of O atoms 2 C6 H10 O5 + x O2 ---> 12CO2 + 10 H2O now O balance 10 + 2x = 24 + 10 x = 12 2 C6 H10 O5 + 12 O2 ---> 12CO2 + 10 H2O

**MATH WORD PROBLEM**

b+c = 420 so c = 420 - b c = (3/4) b so 3 b/4 = 420 - b 3 b = 1680 - 4 b 7 b = 1680 b = 240 bears total b = sb + bb but bb = (9/7)sb so 240 = sb +(9/7) sb = (16/7)sb sb = 105 small bears bb = 240 - 105 = 136 big bears I will leave the last part for you

**Chemistry**

2 * 7.9 = 15.8 mols C 15.8 * 12 g/mol = 189.6 grams of carbon

**whoops**

we got carbon as a result of step 2 so we could put it back in to step 1 then we would only need two carbons fo each CaCO3

**Chemistry**

In the end for the carbon 3 C --> CO + C + CaCO3 so in the end we need 3 C atoms for every molecule of CaCO3 C = 12 g Ca = 40 g 3O = 3*16 = 48 g so CaCO3 = 100 g/mol so we get 7.90 mols of CaCO3 for that we need 3*7.9 = 23.7 mols of C 23.7 * 12 = 284.4 grams of Carbon

**WORD PROBLEMS UGH**

kiwi need 336 * 6/8 = 252 fruits mango needs 336*3/5 = 202 fruits strawberries 336*5 = 1680 fruits total fruits = 2134

**algebra**

186 n + 30 ???? so what is the question?

**Math please check my answer?**

You are welcome :)

**Math please check my answer?**

By the way: https://www.wolframalpha.com/input/?i=e^%28x-4%29-2+

**Math please check my answer?**

again it has a horizontal asymptote of y = -2 as x--->-oo but is defined for all real x so yes, range is all real x

**math**

There is no sure answer since there is not a constant number of leaves per inch 2/3 = .67 leaves/inch 14/15 = .933 leaves /inch so 6 * .67 = 4.02 6 *.933 = 5.6 leaves per inch so probably more than four and less than 6 try 5 also see: http://www.jiskha.com/display.cgi?id=12608...

**Math**

yes, all real numbers again

**Math**

yes, all real numbers

**Physics**

well, I used 1000 for rho before I saw the hint so you use 1060 rho g h=1000*9.81*.496 = 4.86* 10^3 Pa which is 4.86 k Pa 15.02 - 4.86 = 10.15 k Pa rho g h = 1000*9.81*1.3 = 12.75 k Pa 15.02 + 12.75 = 27.8 k Pa

**algebra**

V = pi r^2 h = pi (D^2/4) H

**Math**

None of the functions you have listed seem to have zero denominators. This function has a horizontal asymptote at y = -1 as x --->-oo but is defined for all real x

**physics**

power = work/time = (25000+800)(30)/60 = 12,900 Watts or about 13 KW

**Math**

sign error add 37 x to both sides f(x) = 37 x + 82

**Calculus**

best use radians, pi/2

**History**

I think she quoted the Preamble to the Constitution.

**physics**

m1 = 40.4 x1 = 0.00 y1 = .403 m2 = 15.2 x2 = .158 y2 = 0.00 m3 = 9.49 x3 = 0.48 y3 = -.210 m = 65.09 kg x cg = [40.4*0+15.2*.158+9.49*.48]/65.09 = 0.107 m y cg =[40.4*.403+15.2*0+9.49*-.21]/65.09 = 0.22 m

**physics**

m=M/10^30 4.19*1.75 = m*(7.78-1.75) = m * 6.03 so m = 1.22 so m = 1.22 * 10^30 kg

**Math ~ Check 1 Answer ~**

You are welcome.

**Math ~ Check 1 Answer ~**

agree

**math**

a^2 + (a+1.05)^2 = 59^2 a^2 + a^2 + 2.1 a + 1.1025 = 3481 2 a^2 + 2.1 a = 3480 a^2 + 1.05 a - 1740 = 0 https://www.wolframalpha.com/input/?i=a^2+%2B+1.05+a+-+1740 a = 41.2 b = 42.2

**physics**

initial momentum = .00626*344 = 2.15 2.15 = .00626 Vb1 + 1.205*.673 Vb1 = 214 m/s exiting first block bullet momentum entering second = .00626*214 = 1.34 1.34 = 1.584 v v = .846 m/s (a) (b)final = (1/2)(1.584)(.846^2) = .567 Joules initial = (1/2)(.00626)(344)^2 =370 ratio = ....

**physics**

77.1 v = .0593 (.263) v = .000202 m/s better look fast because that blood circles around again in the body, reversing momentum :)

**Social Studies**

The way I read it: because accepting heliocentrism implied that the Bible was inaccurate since the Bible seems to support geocentrism

**Social Studies**

Agree about discontented citizens in France. steps?

**Social Studies**

The whole paragraph is about individual rights. It is not about tyranny of the majority,

**World History**

https://www.mtholyoke.edu/courses/rschwart/hist255/kat_anna/napoleon.html

**World History**

They wrecked the democracy. Napoleon just stepped in.

**World History**

No, D

**World History**

The Jacobins were world renowned radicals who turned the French revolution into chaos resulting in the Napoleonic wars and his rise to dictatorship and empire. https://www.mtholyoke.edu/courses/rschwart/hist255/kat_anna/jacobins.html

**Algebra 1**

s + (s+4) = 26 2 s + 4 = 26 2 s = 22 s = 11 which is luckily within our allowed domain :)

**Physics**

negligible :) F = G M1 M2 / d^2 F = 6.67 * 10^-11 * 443 * 356 /11.56 F = 91,000 *10^-11 = 9.1 *10^-7 Newtons

**This is madness**

I do the same question over and over. oh well s + (s+4) = 26 2 s + 4 = 26 2 s = 22 s = 11 which is luckily in our domain

**physics**

F = 9*10^9 Q1 Q2 /.16

**math**

Math - Damon, Thursday, March 27, 2014 at 11:57am A wrong .02 * .4 = .008 B wrong .03 * .4 = .012 C wrong .05 * .2 = .01 total wrong = .03 C wrong/total wrong = .01/.03 = .33

**look below**

I just did that

**Math**

A wrong .02 * .4 = .008 B wrong .03 * .4 = .012 C wrong .05 * .2 = .01 total wrong = .03 C wrong/total wrong = .01/.03 = .33

**Math**

x + 210 = 630 x = 420

**History**

Only the second choice makes any sense at all. It worked for Peter the Great.

**same question again ?**

http://www.jiskha.com/display.cgi?id=1395933159

**statistics**

9 people probability of man first = 5/9 then prob of woman = 4/8 so 20/72 for man then woman then probability of woman first = 4/9 then prob of man = 5/8 so 20/72 again add them 40/72 = .55

**physic**

m g = weight = 2*9.81 = 19.62 N static friction max = .8*19.62 = 15.7 N kinetic friction = .65*19.62 = 12.8 N 5 N does not move it. Friction resists with 5 N by third law F - 12.8 = 2 (1.5) F = 15.8 N to get 1.5 m/s^3 acceleration, it is moving now so friction force is -12.8 a...

**Algebra 2**

[ (x-y)(x+2y) ] / [(x+2y)(x+y) ] = (x-y)/(x+y)

**Equation help**

x = [ 6 +/-sqrt(36 -28) ]/2 = 3 +/- sqrt2 = 1.59 , 4.41 number 4

**I did this about ten minutes ago**

Simplify the rational expression (x^2+xy-2y^2)/(x^2+3xy+2y^2) Algebra 2 - Damon, Thursday, March 27, 2014 at 11:04am [ (x-y)(x+2y) ] / [(x+2y)(x+y) ] = (x-y)/(x+y)

**Dimensionless parameters**

You are welcome :)

**Dimensionless parameters**

By the way if gravity had been important (waves), we would have also found the Froude number v/sqrt(gL)

**Dimensionless parameters**

d/H had better be the same for model and experiment If viscosity were important then rho vL/mu, the dimensionless Reynolds number should be the same, but the problem statement says mu is not important so we are left with d/H and the ratio of force to other parameters which we ...

**CALCULUS problem**

int x^-3 dx = -.5 x^-2 + c at x = 3 = -.5/9 at x = 1 = -.5 so A = .5 - .5/9 = .5(8/9) = 4/9 B at x = h int = -.5/h^2 right half = -.5/9 +.5/h^2 left half = -.5 h^2 +.5 so -.5 h^2 + .5 = -5/9 +.5/h^2 1/h^2 = .5 + 5/9 = 4.5/9 + 5/9 = 9.5/9 = 19/18 int 1 to 3 of pi (x^-6)dx = -pi...

**who dare to give the answer!**

I not only do not dare, I do not have the slightest idea what you are talking about.

**Math**

I am not familiar with the notation but what happens is (x , y) --->(x , -y) so I would choose C.

**makes no sense**

Please check what you typed.

**typo**

same volume both times

**maths**

p = 2000 + 100 x - 6 x^2 if x = 25 p = 2000 + 2500 - 3750 p = 750 not a wise decision unless there is a typo

**math**

Well, let's hope we are right :)

**math**

surface area = 4 pi r^2 so dv/dt = 4 pi r^2 dr/dt dv/dt = 75 cm^3/s so dr/dt = 75/(4 pi r^2) when r = 5 dr/dt = 3/(4 pi) = .75/pi cm/s after 60 seconds volume = 75*60 = 4500 cm^3 (4/3)pi r^3 = 4500 pi r^3 = 3375 r = 15/pi^(1/3) r^2 = 225/pi^(2/3) 4 pi r^2 = 900 pi^(1/3) dr/dt ...

**social study**

http://gloucester-ma.gov/index.aspx?nid=649

**social study**

here's one here: http://wgbhnews.org/post/wind-turbines-power-gloucester-city-buildings

**Calculus**

huh?

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