Thursday

July 30, 2015

July 30, 2015

Total # Posts: 21,577

**physics**

m g h = (435-205) h = (435-25)/( 30*9.81)
*June 21, 2015*

**physics**

initial Ke = (1/2)(54.5)(1.95)^2 = 104 J energy added = 80-265 = - 185 J so if no change in elevation final ke would be 104-185 = - 81 J actual final ke = (1/2)(54.5)(5.95)^2 = 965 J so the gravitational PE loss (dropped down to gain speed) = 965 + 81 = 1046 J or delta PE = -...
*June 21, 2015*

**physics**

work done by push = 154 * 6.4 J positive work done by friction = -50*9.81*.24*6.4 J negative work done by normal = work done by weight = ZERO because force perpendicular to displacement
*June 21, 2015*

**World War 2**

Google "peace in our time "
*June 21, 2015*

**physics**

oh well, I suppose I can pretend to know what the question is. v = vertical speed Vi = initial vertical speed so Vi = 10 sin 53.1 How long rising? v = Vi - g t = Vi - 9.81 t at top, v = 0 so tt = Vi/9.81 at the top (calling tt the top time) How high at top? h = 24 + Vi tt - 4....
*June 21, 2015*

**math**

Your initial velocity component up which you are calling Vo is 1750 sin 10 so Vo = 304 ft/s ( I can hardly believe you are using feet not meters but well here g will be 32 ft/s^2) Your distance down range, x = u t where your constant horizontal speed u = 1750 cos 10 (that is ...
*June 21, 2015*

**Math**

Oh and also it is imaginary for (2-x) negative or x > 2 In other words the new inverse curve is open to the left with a vertex at (2,-3)
*June 21, 2015*

**Math**

well, first of all that is a parabola as you know. If you invert it, it is likely to have two values of the ordinate for every value of the abscissa. In other words the inverse will not likely really be a function. However to do what you want to do, use x for y and y for x and...
*June 21, 2015*

**Chemistry**

nah, 10^23/10^23 = 1 perhaps write it as (6.70/6.02)(10^23/10^23) * 18.02
*June 21, 2015*

**Math 11 u**

Or now that I know the answer: w^2 + 4 w - 117 = 0 (w-9)(w+13) = 0
*June 21, 2015*

**Math 11 u**

w^2 + 4 w - 117 = 0 Do you know how to use the quadratic equation? w = [ -4 +/- sqrt (16 + 468) ] /2 w = -2 +/- (1/2) sqrt 484 ) w = -2 +/- (1/2)22 w = -2 +/- 11 use the + root w = 9 then L = 13 ============== check 9 * 13 = 117 sure enough
*June 21, 2015*

**Chemistry**

Fe = 56 2N =2*14 = 28 6O = 6*16 = 96 so the stuff is 180 grams/mol .555 * .650 = .361 mols present .361 * 180 = 65 grams
*June 21, 2015*

**Physics**

both go distance d car A takes time t car b takes time (t - 1) d = 50 t d = 60 (t - 1) so 50 t = 60 t - 60 10 t = 60 t = 6
*June 21, 2015*

**Typos, math, physics**

Would everyone who posted math and physics problems this morning please go back and check for typos? It is difficult to guess what you mean and we do not have your text book.
*June 21, 2015*

**Nobody knows**

You did not tell us: 1. radians per second or rpm or something about speed. 2. jow high the axis of the wheel is.
*June 21, 2015*

**chem**

http://www.google.com/search?q=potassium+carbonate+formula&ie=utf-8&oe=utf-8
*June 21, 2015*

**chem**

CO3-- is negative two In other words it has two more electrons than protons K + is plus one. in other words it is missing an electron To make it all come out a neutral solid salt you need two K ions for every one carbonate ion so K2CO3 GOOGLE potassium Carbonate https://www....
*June 21, 2015*

**physics**

kg * m/s * m/s = kg m^2/s^2 By the way force = mass * acceleration which is kg m/s^2 in Newtons force * distance = work which is energy in Joules so energy = kg m/s^2 * m = kg m^2/s^2
*June 20, 2015*

**Algebra**

The y axis intercept is when x = 0 Here when x = 0 y = (-3)^2(-9) = 9 * -9 = -81 The x intercepts are when y = 0 which is when x = 3 (just barely hits the axis) and when x = 9 On the right is when x is very large positive. That is y ---> x^2 (x) = x^3 rising on the left x ...
*June 20, 2015*

**homewrok**

(tagged/total) = (8/60)= 200 / x 2/15 = 200/x 1/15 = 100/x x = 1500
*June 20, 2015*

**Calculus**

Perhaps you mean x = delta x = 1 ??? y = 7 x^-1 dy/dx = 7 (-1)x^-2 = -7 x^-2 if x = 1 y = 7/1 = 7 dy/dx = -7 delta y = -7 delta x if delta x = 1 delta y = -7 Y + delta Y = 7-7 = 0 real answer y (2) = 7/2 = 3.5
*June 20, 2015*

**ALGEBRA**

let age = x x/4 + x/5 + x/3 + 13 = x LCD = 60 60 x/4 + 60 x/5 + 60 x/3 + 13*60 = 60 x 15 x + 12 x + 20 x + 13 * 60 = 60 x 47 x + 13 * 60 = 60 x 13 x = 13 * 60 x = 60
*June 20, 2015*

**physics**

It fell 100 meters. h = (1/2) g t^2 100 = 4.9 t^2 t = 4.52 seconds
*June 20, 2015*

**Physics**

yes If you were a ship designer you would know that for a model and full scale under gravitation v/sqrt(gL) is the same model and full scale. if you divide the lengths by 100, you divide the speeds by 10 Google Froude number - here : http://www.engineeringtoolbox.com/froude-...
*June 20, 2015*

**Physics**

The forces will certainly not be the same but much smaller on the model. The acceleration is the question. h = H/10^2 m = M/10^6 because volume is 1/100^3 V = sqrt (2 g H) v = sqrt (2 g h) so v = V/10 acceleration is velocity /time time is distance/velocity so acceleration = k...
*June 20, 2015*

**Physics**

mass = 9/g = 9/9.81 kg = .917 friction or other force holding it back = 15 Newtons so F - 15 = ma = .917 (a) but a = 14/4 so F = 15 + .917(14/4) = 18.2 N
*June 19, 2015*

**Physics**

F = m g down - 40 up = 10(9.81)-40 = 58.1 N down a = F/m = 58.1/10 = 5.81 m/s^2 down
*June 19, 2015*

**math**

Note Mathmate response to the question below titled Calculus AB
*June 18, 2015*

**math**

be careful with parentheses like use dy/dx= (x^2+3y^2)/ ( 2xy ) http://www.wolframalpha.com/widgets/view.jsp?id=e602dcdecb1843943960b5197efd3f2a y = +/- x (cx-1)^.5
*June 18, 2015*

**Math**

s = 2 f/3 s = 4 (f+5) /7 -------------------- 2 f/3 = 4 f/7 + 20/7 2*21 f/3 = 4*21 f/7 + 20*21 /7 14 f = 12 f + 60 2 f = 60 so f = 30 s = 2 f/3 = 20 ======================= check s/f = 20/30 = 2/3 yes s/(f+5) = 20/35 = 4/7 yes, it worked
*June 18, 2015*

**stats**

http://davidmlane.com/hyperstat/z_table.html
*June 18, 2015*

**Chemistry**

CH3CH2OH + 3O2 => 2CO2 + 3H2O CH3CH2OH is 2*C = 24 + 6*H = 6 + 1*O = 16 = 46 grams/mol so that is 775/46 = 16.85 mols of ethanol so we would get 2*16.85 = 33.7 mols of CO2 CO2 = 12+32 = 44 grams/mol 33.7 *44 = 1483 grams of CO2 Oh my, greenhouse galore
*June 18, 2015*

**Public speaking**

https://www.google.com/search?q=articulate+definition&ie=utf-8&oe=utf-8
*June 18, 2015*

**Public speaking**

I am having trouble articulating a reply.
*June 18, 2015*

**Math Trigonometry**

tan angle = 6/8 = .75
*June 18, 2015*

**science**

For example from that link: " Reason #1: Without wolves and other large predators, ecosystems can go haywire. A 2001 study (PDF) found that when wolves went extinct in Yellowstone, for example, the moose population ballooned to five times its normal size and demolished ...
*June 18, 2015*

**science**

Here, click through these 10 pictures http://www.motherjones.com/slideshows/2011/04/wolves-protect-climate-change/seated-gray-wolf-yellowstone
*June 18, 2015*

**science**

The animals the lynx eats would get more numerous. The plants and animals that those target animals eat would get scarcer. Whatever they in turn feed on multiplies. The effects work down from that top predator and equilibrium populations of everything in the forest changes. ...
*June 18, 2015*

**physics**

v = Vi - g t here Vi = 150 sin 30 = 75 m/s at top v = 0 0 = 75 - 10 t solve for t at top t = 7.5 seconds then if they ask for the height h = (1/2) g t^2 to fall from top = 5 * (7.5)^2 then if they ask for range u = 150 cos 30 range = u t = 150 cos 30 * 7.5 * 2 the 2 is because...
*June 18, 2015*

**Math (PLEASE HELP!)**

divide length dimension by sqrt 2 to get half the area
*June 18, 2015*

**Math (PLEASE HELP!)**

w(w+5) >/= 84 w^2 + 5 w - 84 >/= 0 solve for zero, anything bigger works w = [ -5 +/- sqrt(25 + 336) ]/ 2 w = [ -5 + 19 ]/2 = 7 then L = 12 so anything at least 7 by 12
*June 18, 2015*

**Math (PLEASE HELP!)**

parabola opens down (sheds water) when is it between the vertex and 22 feet? 16 t^2 - 42 t - 3.75 = -22 16 t^2 - 42 t + 18.25 = 0 t = [ 42 +/- sqrt (1764 - 1168) ] / 32 t = [ 42 +/- 24.4 ] /32 t = .55 to 2.07 seconds
*June 18, 2015*

**physics**

or in other words half the radius -->4 g then 4 times the earth mass --> another 4 times g
*June 18, 2015*

**physics**

mstudent = 810/9.81 = 82.6 kg THE MASS, m in kg, DOES NOT CHANGE WITH g, ONLY THE WEIGHT F = G * Mplanet* mstudent /r^2 on earth 810 = G Mearth * mstudent /rearth^2 on Nerdland F = G Mnerd *82.6 / rnerd^2 so F = G (4 Mearth) * 82.6 / (.25 rearth^2) F = 16 G Mearth * 82.6 /...
*June 18, 2015*

**PHYSICS**

(1/2) m Vi^2 + m g h = (1/2) m Vfinal^2 or Vfinal^2 = Vi^2 + 2 g h = 225 + 2 (9.81)(20) = 617.4 sqrt 617.4 = 24.8
*June 18, 2015*

**physics**

a - gravity down, air friction up b - friction force exerted on roadway by horseshoe, equal and opposite force exerted by horseshoe on roadway, horse then exerts pull on shaft, shaft pulls back on horse and forward on cart, roadway exerts friction force back on cart c - ...
*June 18, 2015*

**System of Equation**

That is substitution.
*June 18, 2015*

**physics**

As I said a few minutes ago, you try first.
*June 15, 2015*

**Physics**

delta L/L = (1.1*10^-5)(45) = 49.5 * 10^-5 meters/meter of hypothetical stretch that delta L/L is strain delta L/L = sigma/E which is stress/young's stress = 4.95*10^-4 * 2*10^11 = 9.9 *10^7 N/m^2 tension = stress * area =9.9*10^7 * 4*10^-6 = 396 N b) well we got 9.9*10^7 ...
*June 15, 2015*

**physics**

Just like the balloon A and B problem. I will be happy to review your results.
*June 15, 2015*

**physics**

Now Alex, enough already, draw picture with all forces. There is one, the weight F = - m g so F = m a = - m g so a = -g THE WHOLE TIME, NOT JUST AT TOP Now no more questions until you try yourself !!!!
*June 15, 2015*

**algebra 2**

GRAPH IT !!!!! when x = 5 , f(5) = 25 when x = 2 , f(2) = 4 check when x = -2 , f(-2) = -4 when x = 1 , f(1) = 5 check
*June 15, 2015*

**physics**

huh? 5 + 7.5
*June 15, 2015*

**physics**

well, do the power thing first v = 0 + a t v = Vi = 20 * 4 = 80 m/s at power cutoff at what height did the power stop? h = 0 + 0 t + (1/2)(20)(16) = 160 meters so we have Vi = 80 m/s at Hi = 160 meters now coast up v = Vi - g t at top v = 0 , using g = 9.8 0 = 80 - 9.8 t t = 8...
*June 15, 2015*

**algebra2**

well, let's look at the zeros first x(x^2-9) - 1(x^2-9) = 0 (x-1)(x-3)(x+3) = 0 so y = 0 for x = 1 and for x = 3 and for x = -3 that is three values of x for a single value of y, not a good symptom.
*June 15, 2015*

**Calculus**

The max is where |sin x| = 1, cos x = 0 the min is where sin x = 0, |cos x| = 1 but really all you really have to say is |sin x | </= 1 so |sin^2 x| </= 1 so max is 1 and that is when |sin x|=1
*June 15, 2015*

**Calculus**

You already did it. f(0) = 0 f(pi) = 1 etc, at the four points where the derivative is zero
*June 15, 2015*

**Calculus**

You mean cos x sin x = 0 when cos x = 0 or when sin x = 0 when cos x = 0, then sin x = 1 and you have a max when sin x = 0, then cos x = 1 and you have a min
*June 15, 2015*

**Calculus**

LOL, |sin x| is always </= 1 it is at + pi/2 and 3 pi/2 where cos x , the derivative of sin x, is 0
*June 15, 2015*

**physics**

I also get -0.0391
*June 14, 2015*

**physics**

I am not going to answer the others because they are really the same as this one. For example if you have charges 2q and - 2q within a closed surface, the net E flux out is zero.
*June 14, 2015*

**physics**

The Gauss' Law flux = integral E dot dA = Q/epsilon The Gauss law states that electric net flux through any Gauss surface is directly proportional to the net charge enclosed by the surface where is permittivity of vacuum
*June 14, 2015*

**physics**

Huh ?? Gauss! Does not matter shape or size of surrounding surface. Flux out proportional to charge inside.
*June 14, 2015*

**physics**

if you have Q per square meter (maybe call it sigma) net flux out of the square meter is Q/epsilon Looking at both sides of the sheet we have surface area of the enclosure = 2 square meters flux = E * 2 m^2 = Q/epsilon
*June 14, 2015*

**Algebra2**

2(3x-5)= 16 6x -10 = 16 6 x = 26 x = 13/3 and 2(-3x+5) =16 -6x + 10 = 16 6 x = -6 x = -1
*June 14, 2015*

**geometry**

meters, seconds, g = 9.8 m/s^2 h = Vi t - 4.9 t^2 tan q = h/x so x tan q = Vi t - 4.9 t^2 observe angle q at time t solve for x at time t or if Vi is the unknown solve for Vi at x and t then solve for h
*June 14, 2015*

**Calculus**

I have no idea where Q is
*June 13, 2015*

**Calculus**

4 s + 2w + 4w = 4 s + 6 w = 17 A = s^2 + w(2w) = s^2 + 2 w^2 s = (17-6w)/4 A = (1/16)(17-6w)^2 + 2 w^2 dA/dw = 0 at min 0 = (1/8)(17-6w)(-6) = 4 w (3/4)(17-6w) = 4 w 3 (17-6w) = 16 w 51 - 18 w = 16 w 34 w = 51 w = 51/34 = 1.5 then find s and w and 2 w
*June 13, 2015*

**Pre-Calculus**

we want (x-h)^2/a^2 +(y-k)^2/b^2 = 1 now x-h = a cos t so (x-h)^2 = a^2cos^2 t so (x-h)^2/a^2 = cos^2 t similarly (y-k)^2/b^2 = sin^2 t so (x-h)^2/a^2 + (y-k)^2/b^2 = cos^2 + sin^2 = 1
*June 13, 2015*

**typo**

but we know t = 19.5/x should be t = x/19.5 of course
*June 12, 2015*

**Physics**

Horizontal, no force, u =constant so x = 19.5 t so t = x/19.5 Vertical, f = -9.81 m/s^2 * mass = m a so a = acceleration = - 9.81 so a = -9.81 v = Vi - 9.81 t v = 15.4 - 9.81 t then y = initial height + 15.4 t - 4.9 t^2 call initial height of quarterback hand Hi y = Hi + 15.4 ...
*June 12, 2015*

**Physics**

I do not care if she is thin or fat. falls 9 meters, how long? h= (1/2) g t^2 18 = 9.8 t^2 t = 1.36 falling goes 1.75 meters horizontal in 1.36 seconds 1.75 = u t = u (1.36) u = 1.29 m/s horizontal speed
*June 12, 2015*

**Physics**

This is not Physics. tourist runs distance d bear runs distance (d+31.1) same time t d = 3.24 t d+31.1 = 4.5 t so d + 31.1 = 4.5(d/3.24) 3.24 d + 100.7 = 4.5 d d = 80 meters max this tourist is no track star :(
*June 12, 2015*

**Alg 2 HELP!**

-5, 1 , 2 http://www.wolframalpha.com/widgets/view.jsp?id=a7d8ae4569120b5bec12e7b6e9648b86 (right away you should see that one works, then you have a quadratic) domain of parabola is all real x. (range is another story) g = (2x+1)^2 + 3(2x+1) now you multiply out and collect ...
*June 12, 2015*

**alg 2**

Yes it is (x+4)(x^2+9) x = -4 you know however x^2+9 = 0 x^2 = -9 is x = +3i or x = -3i (not rational real)
*June 12, 2015*

**Alg**

http://www.mathportal.org/calculators/polynomials-solvers/polynomial-graphing-calculator.php
*June 12, 2015*

**math**

4 is not it I think but 3 kind of looks reasonable
*June 11, 2015*

**math**

in this system of units, remembered only by ancient mathematicians, g = 32 ft/s^2 approximately. so a = - 32 v = Vi - 32 t = 38 - 32 t h = Hi + Vi t + (1/2) a t^2 0 = 30 + 38 t - 16 t^2 or 16 t^2 - 38 t - 30 = 0 8 t^2 -19 t -15 = 0 solve that quadratic for t, use the positive ...
*June 11, 2015*

**geometry**

think square 3 meters on each side area = 3*3 = 9 then square 6 meters on a side, double area = 6*6 = 36 or four times length ratios = 2 area ratios = 4 2^2 = 4
*June 11, 2015*

**geometry**

areas scale as square of length ratio so 5/2 in area ---> sqrt(5)/sqrt(2) in length so 25 * sqrt 2/sqrt 5 = 15.813883
*June 11, 2015*

**Bayes' Theorem**

say 100 students 40 from Ka .04*40 = 1.6 fails 50 from Ill .02 * 50 = 1 fails 10 from Oh .06 * 10 = .6 fails total failures = 1.6+1+.6 = 3.2 That is 3.2/100 = 3.2 % = .032 3.2 fail, 1.6 of whom are from Ka 1.6/3.2 = .5 or 50% BUT you said use Bayes so P(Ka if failed) =P(failed...
*June 11, 2015*

**physics**

melting ?
*June 10, 2015*

**Math117A**

height/shadow = 4.2/12.6 = 20.4 /x 4.2 x = 12.6 * 20.4 x = 12.6 * 20.4 / 4.2 x = 61.2 check, the shadow should be about three times as long as the object is high in this problem. It is.
*June 10, 2015*

**algebra2**

3 x - 10 x - 20 = 13 - 7 x - 7 x = 33 - 7x 0 = 33 no solution please try these and post your attempt. I am getting bored.
*June 10, 2015*

**algebra2**

x = -22 You can solve that :) Now Karla, try the problem before posting it.
*June 10, 2015*

**algebra2**

10 x + 30 = 10 x + 30 ANY value of x works INFINITE number of solutions BUT what if it were 10 x + 30 = 10 x + 40 then there would be no solutions at all
*June 10, 2015*

**Finite Math**

You are welcome :)
*June 10, 2015*

**Finite Math**

100 students 50 had pre calc - 15 got A, 35 not A 50 no pre cacl - 10 got A, 40 not A sure looks like 35 of the hundred :)
*June 10, 2015*

**algebra2**

2 x = 145 so x = 145/2 the end
*June 10, 2015*

**chemistry**

by the way http://www.quora.com/How-much-water-can-you-split-into-hydrogen-and-oxygen-using-electrolysis-with-one-kilowatt-hour-of-electricity
*June 10, 2015*

**chemistry**

3 hours * 3600 seconds/hour = 10800 seconds 10800 seconds * 0.1 amps = 1080 Coulombs H2O --> 2H+ + O-- 1 mol electrons = 96,500 Coulombs so 1080 C * 1/96500 = .0112 mol electrons looking at equation, we need 2 mol electrons for every mol of H2 so we get .0056 mol of H2 ....
*June 10, 2015*

**science**

Draw a sketch diagram 2 * 5 cos 30 = 8.66 m/s at 30 degrees to each
*June 10, 2015*

**Chemistry**

Ni is about 68.7 grams per mol. so 138/68.7 = 2.008 mol of Ni that is 2.008 mol * 6.02*10^23 atoms/mol = 12.1 *10^23 atoms (quite a few )
*June 10, 2015*

**Chemistry**

by the way iron is also about 8 times as dense as water (1 g/cc or 1000 kg/m^3) and aluminium is less and concrete is about half. That gives you a bit of a check.
*June 10, 2015*

**Chemistry**

That looks right to me.
*June 10, 2015*

**Math**

Iris, You had your choice of 6% compounded or 13% simple for four years. 13% simple wins.
*June 10, 2015*

**Math**

when you compound at interest rate x percent every period you multiply by (1+x/100) so for 4 years at 6% multiply four times by (1 + .06) which is the same as multiply by 1.06^4 if it were 6% per year compounded monthly thet would be 6%/12 per month .06/12 = .005 so we would ...
*June 10, 2015*

**Math**

Well how did you do it really ?
*June 10, 2015*

**Math**

13% is so much more than 6% that the compounding will not catch up for many years.
*June 10, 2015*

**Math**

1.06^4 = 1.26248 *2000 = 2524.95 so earned 524.95 0.13 * 4 =.52 .52 * 2000 = 1040 so earned 1040.00 go with the 13 % simple
*June 10, 2015*