Thursday
July 30, 2015

# Posts by Damon

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
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
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

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

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

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

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