Tuesday

September 1, 2015
Total # Posts: 21,834

**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*

**Chemistry**

how many Joules do you need? Joules needed = specific heat * mass * change in temp then watts * seconds = Joules needed
*June 9, 2015*

**Chemistry**

C * m (60-40) = C * 50 (40-20) so m = 50 grams or .050 Kg
*June 9, 2015*

**History**

Should I laugh or cry?
*June 9, 2015*

**Calc 1**

sure looks like it to me
*June 9, 2015*

**Calc 1**

Hey, you can google too :)
*June 9, 2015*

**Calc 1**

not necessarily http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=9&cad=rja&uact=8&ved=0CEgQFjAI&url=http%3A%2F%2Fwww.mathsisfun.com%2Fcalculus%2Fdifferentiable.html&ei=2wt3VbzLIMGasQXEoIEI&usg=AFQjCNG-Oqx8EjGrCBl7-c8WA0YYFZ28ag&sig2=WquSfxU_It3cBOBGKCGExg&bvm=bv....
*June 9, 2015*

**Calc 1**

True, if more then not a function http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=3&cad=rja&uact=8&ved=0CDMQFjAC&url=http%3A%2F%2Fwww.milefoot.com%2Fmath%2Fcalculus%2Flimits%2FFindingAsymptotes12.htm&ei=ZAt3Ve-jC4mQsAXlt4HgDQ&usg=AFQjCNHZjboUch1fdELGYXBuIZC-Tnu_rg...
*June 9, 2015*

**Calculus 1**

well, if x = .99 I get 1.50 if x = .999 then 1.500 that is because numerator = (x-1)(x+2) denominator = (x-1)(x+1) so what we really have is (x+2)/(x+1) which is 1.5 at x = 1 It is true that the original function is undefined at x = 1
*June 9, 2015*

**physics**

They are brakes. after 5 sec at constant v Vi = 20 v = 20 + a t where t is total time - 5 v = 0 when t = 8 so 0 = 20 + a (8) a = -20/8 = - 5/2 so v = 20 - (5/2) t = 20 - (5/2)(time - 5)
*June 9, 2015*

**Math**

11 with vanilla + 11 with chocolate = 22 , right
*June 9, 2015*

**Calc 1**

y at x = 5 = a then y^2 = 25 all right when x = 5
*June 9, 2015*

**math**

total N = 330 + 900 = 1230 Total E = 640 + 370 = 1010 so sqrt (1230^2 + 1010^2)
*June 9, 2015*

**Calc 1**

nope, what if y = L (x-a)/|x-a|
*June 9, 2015*

**Math**

pi is actually about 22/7 This problem is a lot harder than it looks because you should really pack the discs in a hexagonal pattern but I suspect the best we can do is put squares around the circles. 100 /14 = 7.14 so 7 lengthwise 60/14 = 4.28 so 4 that direction 7 * 4 = 28 ...
*June 9, 2015*

**math trigonometry**

I have no reason to believe it is true.
*June 9, 2015*

**SCIENCE**

A to B speed = 300m/170 seconds velocity = speed if that direction is + then A to C distance = 300 + 100 = 400 average speed = 400/230 but total displacement = +300 - 100 = 200 so'=average velocity = 200/230
*June 9, 2015*

**math**

I do not think so. Sketch a graph.
*June 8, 2015*

**Physics**

x = 1.40 t^2 - .0505 t^3 at t = 0, x = 0 at t = 1.91, x =1.40 * 1.91^2 - .0505 * 1.91^3 = 4.755 meters so 4.755 meters in 1.91 seconds = 2.5 m/s do the others the same way, find out how far it went in the time interval and divide by the time interval
*June 8, 2015*

**statistics**

5/15 * 4/14
*June 8, 2015*

**MATH**

x/10 = 37/8 so x = 370/8 (370/8)/16 = 370/128 = 2 114/128 = 2 57/64
*June 8, 2015*

**math**

2* (1/2) pi (1) + 2*3 maybe ?
*June 8, 2015*

**Math help please.**

7 yes 8 A because -3 * -2 = +6
*June 8, 2015*

**Math help please.**

6)-2r(8r+5) A)-16r^2+5 B)-16r+10 C)-16r-10r** D)-16r-10 Nah, -16 r^2 - 10 r probably c but a typo
*June 8, 2015*

**Math help please.**

7^4/7^2 = 7^2 = 7*7 = 49 right
*June 8, 2015*

**Math help please.**

4) 50 A)0 B)5 C)1 D)-5 Perhaps you mean 5^0 but anything^0 = 1
*June 8, 2015*

**Math help please.**

3) 4^4/4^6 4 - 6 = -2 4^-2 = 1/4^2 = 1/16 A)-16 B)16 C)1/16 D)-1/16
*June 8, 2015*

**Math help please.**

2) h^14/h^5 14 - 5 = 9, not 19
*June 8, 2015*

**Math help please.**

1) x^9/x^2 = x(9-2) = x^7
*June 8, 2015*

**maths**

if the second hand moves 180 degrees, that is half a minute .5 min (360 degrees/60 min) = 3 degrees
*June 8, 2015*

**Calculus**

Oh, go with what Steve said.
*June 8, 2015*

**Calculus**

profit = p(x) - C(x) = 50-.01 x - 10 - 2x = 40-2.01 x max at x = 0 I bet you have a typo though.
*June 8, 2015*

**math**

well one way is a parabola write a parabola that goes through (4,1) (6,1.5) and (8,6) first (4,3) (6,0) and (8,0) Y1 = 3(x-6)(x-8) /(4-6)(4-8) = 3(x^2 -14 x + 48)/ 8 second (4,0)(6,1.5)(8,0) Y2 = 1.5 (x-4)(x-8)/(6-4)(6-8) = -(1.5 x^2 -18 x +48)/4 third Y3 = 6(x-4)(x-6)/(8-4)(8...
*June 7, 2015*

**math**

whoops, I dd it for 300 of fence, not 200
*June 7, 2015*

**math**

if two internal petitions the 4 x needed for cross fencing + 2 L needed for length P = 4 x + 2 L =300 or L = 150 - 2 x A = x L = x (150 - 2 x) = 150 x - 2 x^2 if you know calculus: dA/dx = 0 at max = 150 - 4 x so x = 150/4 = 37.5 then L = 150 -2*37.5 = 75 AREA = 37.5*75 = 2812...
*June 7, 2015*

**COLLEGE MATH**

I do not know what level of math you are at. If calculus then dC/dx = 0 at min = .4 x =96 so x = 240 If Algebra 2 level then complete the square to find vertex .2 x^2 - 96 x = -12095 x^2 - 480 x + 240^2 = - 60475 x^2 - 480 x + 240^2 = - 2875 (x-240)^2 = -2875 so x = 240 and C...
*June 7, 2015*

**Another math related question**

4/10 * 7/15 = 14/75
*June 7, 2015*

**Calculus**

you have P = 2 x + 154/x BUT you took the derivative incorrectly P' = 2 -154/x^2 so for min or max 0 = 2 - 154/x^2 or x^2 = 77 NOTE d/dx (1/x) = -1/x^2
*June 7, 2015*

**physics**

any acceleration is down the slope, perpendicular to the force we are interested in. That normal force is the component of weight normal to the hill surface which is m g cos 25
*June 7, 2015*

**physics**

If two capacitors are in parallel, they hold more charge for a given voltage. We know that C = Q/V here C1 = Q1/V C2 = C2/V C1 + C2 = (Q1+Q2)/V so final C = C1 + C2 In other words, if in parallel, add capacitances because you add charges per unit voltage
*June 7, 2015*

**to damon**

You are welcome - good luck !
*June 7, 2015*

**algebra**

ah ham you know Pascal's triangle so you know binomial theorem after all now call a = 4 y call b = x then (a+b)^4 = a^4 + 4 a^3b + 6 a^2b^2 + 4 a b^3 + b^4 which is 256 y^4 + 256x +6 (4y)^2 x^2 etc
*June 7, 2015*

**maths**

sin PQR = 300/600 = 1/2 so PQR = 30 degrees that is 30 degrees south of west or 60 degrees west of south which id a compass bearing of 180 + 60 = 240 degrees clockwise from north cos 30 = RQ/600 RQ = 520 m
*June 7, 2015*

**algebra**

no imagine (x-y)^2 it is not x^2 - y^2 but x^2 - 2 x y + y^2 You need the "binomial theorem" If you have learned it your problem is straightforward, follow the recipe. If you have not had it in your course, I feel for you because you will have to do it step by ...
*June 7, 2015*