Thursday

December 8, 2016
Total # Posts: 28,440

**Calculus**

If you use right endpoints for the height of each rectangle, Bob has it I think and the answer would be 8. If you use trapezoids you get a more accurate answer, 9 , but they asked for the inaccurate answer.

*June 17, 2016*

**CALCULUS**

well, try this backwards assuming you answered correctly y = -4 cos [ ln(6x) ] dy/dx = -4 (-sin [ln(6x)]*6/6x = 4 sin [ln(6x)] / x I see nothing wrong with your answer.

*June 16, 2016*

**geometry**

(x+3) / (3x-1) = 1/2 2 x + 6 = 3 x - 1 x = 7 GR = 3(7) - 1 = 20

*June 16, 2016*

**Math**

subtract 3 t from both sides 2 c = 35 - 3 t divide both sides by 2 c = (35/2) - (3/2) t or c = 17.5 - 1.5 t

*June 14, 2016*

**Math**

well, they all amount to the same thing. add -2 x + 5 to both sides 4 x - 2 x = 9 + 5 2 x = 14 x = 7

*June 14, 2016*

**physics**

I believe that is indeed Dr WLS ! To be sure, how did we get to Nova Scotia and back ?

*June 14, 2016*

**physics**

W = k/r^2 dW/dr = -2kr/r^4 dW = - 2 k dr /r^3 ==================== 532 N = k / 3959^2 so k = 532 (3959)^2 so dW=-2 * [532 * 3959^2]* 1/3959^3 dW = -.2687

*June 14, 2016*

**physics**

That is called "extrapolation". The answer is of course "maybe" :)

*June 14, 2016*

**History**

Basically two different political viewpoints but see: http://www.thecanadianencyclopedia.ca/en/article/bomarc-missile-crisis/

*June 11, 2016*

**Two different people misspell the same way?Physiscs**

If same height at both ends, symmetric parabolic path. Goes 100 yards? I guess I use obsolete units, 300 feet and g = 32 ft/s^2 Vi = V sin 80 = .984 V u = V cos 80 = .174 V 300 feet = u t 300 = .174 V t how long does it take? h = Vi t - 16 t^2 h = 0 at start and finish 16 t^2...

*June 11, 2016*

**Science**

Water power is cheaper than coal power. Although building the dam is expensive, the water is considered free there from then on ( I could argue at length about that, being into eating salmon for example but anyway....). Coal must be dug up, oil must be pumped up, gas must be ...

*June 11, 2016*

**Science**

For years, every spring, I counted alewives going up a silly concrete fish ladder around a dam here. I always had the early morning shift and there was one doe who often came out of the woods behind to look over my shoulder at my clipboard. If I moved an eyelash she would ...

*June 11, 2016*

**Science**

They may be invasive from the Atlantic via the canal but they seem to love them on Lake Michigan: http://www.jsonline.com/news/wisconsin/alewife-crash-on-lake-michigan-raises-concerns-for-salmon-fishing-b99592228z1-331900031.html (salmon fishing on lake Michigan ?)

*June 11, 2016*

**Science**

Please just send them here. We work like crazy to let them spawn, then they mix with the full time ocean varieties of herring at sea and get swept up by the pair trawlers. I wonder how they survive in the lakes. They must have adapted to full time fresh water.

*June 11, 2016*

**Science**

The reference also does not mention that instead of a fast running stream with its fast running fish, you now have a completely different ecosystem upstream as well. You have a pond or lake now, and any silt in the flow upstream will settle to the bottom in the still water. ...

*June 11, 2016*

**Science**

I am also into alewives and eels and shad, even sturgeon. Needless to say we fish around here and in fact just finished tearing a dam out here so the fish could get upstream from the ocean to spawn.

*June 11, 2016*

**Science**

.... and those salmon that I always worry about?

*June 11, 2016*

**Physics**

I guess we assume the temp is uniform over the surface as is the incoming power (obviously untrue) 5.67*10^-8 T^4 = 1700 T^4 = 300 * 10^8 T = 4.16 * 10^2 = 416 K 416 - 273 = 143 C Hotter than boiling water. Habitable?

*June 11, 2016*

**Chemistry**

Think table salt, NaCl The Na has given up an electron to the Cl so the Na end of the molecule is charged + while the Cl end of the molecule is charged -. The molecule is "polar". That gives a good grip to the next molecule whose - side sidles up to our + side and ...

*June 10, 2016*

**science**

the mass, density and volume are assumed not to change R is old radius Rn is new radius V = pi R^2 L Vn = pi Rn^2 (1.25) L so 1.25 Rn^2 = R^2 resistance = k *Length/area new area = old are /1.25 new length = old length*1.25 so new redistance = old resistance *1.25/(1/1.25) or ...

*June 10, 2016*

**physics beats me**

no change in momentum on system means no net force on system. Force on left charge same as on right charge but opposite direction so total on system is zero. Horizontal electrical force on each Fe= k Q1 Q2 / d^2 let x = d/2 = distance from center line sin 15 = x/.65 x = .168 ...

*June 9, 2016*

**Math**

Although the easy formula for the area is A = (1/2)b h that does not help much if you do not know the altitude h Use Heron's formula http://www.mathopenref.com/heronsformula.html

*June 9, 2016*

**ok but do not believe you**

(1/7)(8/9) = 8/63 However no way the large takes 7 times as much milk as the medium. You have a typo or something.

*June 9, 2016*

**Algebra**

I get 32% of students with grades of 13.7 or above. try: http://davidmlane.com/hyperstat/z_table.html

*June 9, 2016*

**Physics**

R = 400 meters v = 130,000/3600 = 36.1 m/s Ac = v^2/R = 3.26 m/s^2 Ac/g = mu = 3.26/9.81 = .322

*June 9, 2016*

**math**

P V = n R T p, n and R constant so V1/T1 = V2/T2 T1 = 60 + 273 = 333 deg Kelvin 2 / 333 = 3 / T2 T2 = 999/2 = 500 K 500-273 = 227 deg C

*June 9, 2016*

**geometry**

m = slope = (13-5) / (-6 - 2) = 8/-8 = -1 y = -1 x + b 1 = -1(-3) +b b = -2 so y = -x -2

*June 9, 2016*

**Calc**

cos x dx + x^2 dy + 2 x y dx = 0 x^2 dy = - (cos x +2 xy)dx dy/dx = - (cos x + 2 x y)/x^2

*June 8, 2016*

**MATH**

hypotenuse

*June 5, 2016*

**math**

hypotenuse = sqrt(a^2+b^2)

*June 5, 2016*

**Math**

19 = (1/3) 45 ? try again f = b + 26 yes b+3 = (1/3)(f+3) this was wrong 3 b + 9 = f+3 3 b - f = -6 3b -b - 26 = -6 2 b = 20 b = 10 f = 36 ======================== now 13 = (1/3)(39) yes

*June 5, 2016*

**maths-need help**

the two vectors are the same length, call it 1 Draw coordinate system with a from origin to x = 1 along x axis Now draw b, length = 1, from origin to lower right in quadrant 4 Now complete parallelogram to find a+b and a-b vectors see that for a-b to be length of 1, need ...

*June 5, 2016*

**Collins - dangerous**

Collins, please check your answers.

*June 5, 2016*

**Math**

d/15 - d/20 = 8/60 4 d - 3 d = 8 d = 8 ===================== then Amy takes (8/20)*60 =24 min and Ashley takes (8/15)*60 =32min Indeed difference of 8 min

*June 5, 2016*

**physics**

.72 meters = (1/4) wavelength but wavelength = c T = c/f so 4(.72) = 336/f f = 336/2.88 f = 117 Hz see: http://www.physicsclassroom.com/class/sound/Lesson-5/Closed-End-Air-Columns

*June 4, 2016*

**physics**

50 = Vi t + .5 a t^2 v = Vi + a t = 0 at end so a = -Vi/t = -20/t 50 = 20 t - .5 (20/t)t^2 50 = 20 t - 10 t = 10 t t = 5 seconds a =-20/5 = -4 meters/second^2

*June 4, 2016*

**Physics**

u = 39 cos T 39 = u t = 39 cos T * t t = 1/cosT total time in air rise time = t/2 = 1/(2cosT) vertical problem 0 = 39 sin T - g * 1/(2 cos T) but g/2 = 4.9 m/s^2 4.9/cos T = 39 sin T cos T sin T = 4.9/39 2 sin T cos T = 9.8/39 so sin 2T = .251 2T = 15.55 T = 7.28 degrees

*June 4, 2016*

**Hey**

I did the arrow one, now you do some.

*June 4, 2016*

**PHYSICS**

C = charge/unit voltage 5*10^-6 = Q/V For one volt, capacitor holds 5*10^-6 coulombs of charge

*June 4, 2016*

**physics**

What angle? What is density of fluid?

*June 4, 2016*

**physics**

volume = area of base * height V = pi r^2 h but r = D/2 V = pi (D^2/4) h = (pi/4) D^2 h

*June 4, 2016*

**Science**

By the way human passengers are, about the lowest density cargo you can imagine. They want huge amounts of space for their mass and are usually in a hurry. Therefore they are not ideal ship cargo and passenger ships have huge volumes above water for limited draft and ...

*June 4, 2016*

**Science**

The mass of the ship and cargo are supported by the displacement of water (Archimedes Principle) whereas an aircraft (unless a balloon) is supported by lift which requires power from the engines. Therefore you can move huge masses with a ship that you could never lift into the...

*June 4, 2016*

**Social Studies (Please check these)**

a :)

*June 4, 2016*

**Physics**

No external forces on system so center of mass continues at constant speed of zero so does not move how far did he walk in the canoe? 4.00 - 1.5 = 2.5 m distance he moved * his mass = distance canoe moved * its mass 2.5 *71.9 = 95 x x = 2.5 * 71.9 / 95

*June 4, 2016*

**Math**

boat 1 north 45 cos 70 east -45 sin 70 boat 2 north -57 cos 23 opposite so add east 57 sin 23 opposite so add total north = 15.4 + 52.5 = 67.9 total east = +42.3 + 22.3 = 64.6 total =sqrt(67.9^2+64.6^2)

*June 4, 2016*

**Social Studies (Please read this)**

Post it as a separate question.

*June 4, 2016*

**typo**

The Voting Rights Act attempted to abolish discrimination in voting. The act abolished mandatory literacy tests and other requirements intended to prevent black people from voting. An effect of this act was a tremendous increase in number of minority voters. In 1968, blacks ...

*June 4, 2016*

**Social Studies (Please read this)**

One important right that we have in South Carolina is religious freedom. Another right we have in this state is the right to vote. These rights mean that we allowed these things no matter what. People cannot force a religion on to a person or not allow another to vote. Along ...

*June 4, 2016*

**Social Studies (Please read this)**

The Voting Rights Act attempted to abolish abolish discrimination in voting. The act abolished mandatory literacy tests and other requirements intended to prevent black people from voting. An effect of this act was a tremendous increase in number of minority voters. In 1968, ...

*June 4, 2016*

**Physics I (Classical)**

r = 6.38 * 10^6 * cos 71.6 = 2.01 * 10^6 meters angular velocity = w = 2 pi radians/24 hours *1 hour/3600 seconds = 2 pi / (24*3600) = 7.27 * 10^-5 radians/second so Ac = r w^2 = 2.01*10^6 (7.27)^2*10^-10 m/s^2

*June 3, 2016*

**math plz check ;-;**

A rectangular prism with a length of 6 in, a width of 5 in, and a height of 10 in. first **** 300 in^3 A right cylinder with a diameter of 10 in and a height of 8 in. second about (22/7)(25)(8) = **** 628 in^3 THIS IS BIGGEST A rectangular pyramid whose base has an area of 60 ...

*May 31, 2016*

**Math**

y + 2 x = 4 y x = y + 4.5 so y + 2(y+4.5) = 4y 3 y + 9 = 4 y y = 9 x = 13.5

*May 31, 2016*

**CHECK my world history answers**

Google Peace with Honor !!!!!

*May 31, 2016*

**evaluate exptessions**

nothing you can do unless you know x, y and z

*May 31, 2016*

**did you take the first ones out?**

If you do the second time completely new after putting the first bunch back in and mixing them up, then the two experiments are independent. Now what is probability of <.36 with mean of .3 and sd of .045? David lane: http://davidmlane.com/hyperstat/z_table.html .9088

*May 31, 2016*

**Math**

2^3/3^3 = 8/27

*May 31, 2016*

**Math**

base is 6*6 area = 6*6 *2 + 6*h *4 = 360 72 + 24 h = 360 h = 12

*May 31, 2016*

**been there**

done that

*May 31, 2016*

**geography**

3.65^(1/3) (3650/1000)^(1/3) (1/10)(3650)^(1/3) hhmmm try 12 nope try 15 -->225*15 -->3375 close so about 1.5 try1.55 3.72, not going to get much closer than 1.55 without calculator

*May 31, 2016*

**geography**

slope = [ -5 - 1 ] / [ 2 - 4 ] = -6/-2 = 3 = m in y = m x + b so y = 3 x + b put in (4,1) 1 = 3 (4) + b 1 = 12 + b b = -11 so y = 3 x - 11 NOW find line through the middle and perpendicular middle x = (1/2)(4+2)= 3 middle y = (1/2)(1-5) = -2 so through (3,-2) slope = -1/3 so y...

*May 31, 2016*

**tripz**

(1/10) (3570)^1/3 = (1/10)(15.3) = 1.53 approx

*May 31, 2016*

**Physics**

V = Vi up and u horizontal u = V cos 30 = .866 V Vi = V sin 30 = .5 V in air t seconds horizontal problem: 12.2 = u t 12.2 = .866 V t V t = 14.1 so 2Vi t = 14.1 and Vi t = 7.05 vertical problem h = Vi t - 4.9 t^2 = 0 at start and finish 0 = 7.05 - 4.9 t^2 t = 1.2 seconds in ...

*May 31, 2016*

**Science**

Despite Einstein, at this sort of speed and size, mass does not disappear. It is conserved 5 grams of anything mixed with 20 grams of anything is 25 grams of the mixture. Now of course volume is not necessarily conserved, and the volumes would not necessarily add. (some of the...

*May 25, 2016*

**Math**

http://davidmlane.com/hyperstat/z_table.html

*May 25, 2016*

**Math**

L (2 L/3) = 1734 so 2 L^2/3 = 1734 L^2 = 3*1734/2 L = sqrt (2601)

*May 25, 2016*

**Math**

p = k/v or p v = k so P2 V2 = P1 V1 P2 = (V1/V2) P1 P2 = (108/432)(104)

*May 25, 2016*

**English**

There are many famous places in Busan. I'd like to introduce two of them. One is Busan Children's Grand Park in Busanjin-gu. Many kids and their parents visit the park to have a good time. Children can ride a ROLLER COASTER. It is thrilling to be in a Roller Coaster. ...

*May 25, 2016*

**Math-Algebra**

yard area = 42 x^2 fountain area = pi r^2 = pi (4x^2) so remaining area = (42 - 4pi)x^2

*May 24, 2016*

**Math**

10 times 2

*May 24, 2016*

**where are your thoughts?**

I am sure most of us, teachers or not, could answer a lot of these questions even without Google. Please try before you ask us.

*May 23, 2016*

**Algebra**

started with 9 balls, five of them are yellow 5/9 then we have 8 balls, four of them are yellow 1/2 so 5/9 * 1/2 = 5/18

*May 22, 2016*

**physics**

.3 (50-30)(4.2) - m (100-50)(4.4) .3(20)-m(50) m = .12 kg = 120 g

*May 22, 2016*

**physics**

friction force up slope = .24 m g cos A gravity down slope = m g sin A m (2.2) = m (9.81)(sin A - .24 cos A) sin A - .24 cos A = .224 well I can make a table A, left side 0, -.24 5, .083 10, .17 15, .254 so between 10 and 15 deg 13, .22 13 degrees is very close try 13.2 13.2...

*May 22, 2016*

**typo**

I strongly suspect they mean: -2, -12, -72, -432 If my suspicion is correct you have a geometric sequence with a = -2 and r = 6 the next terms are -2 * 6^4 -2 * 6^5 -2 * 6^6 or -2592 -15552 -93312

*May 22, 2016*

**physics**

42 = Vo t + 4.9 t^2 Vo = speed sin 40 36.7 = u t u = speed cos 40 so speed * t = 36.7/cos 40 so speed * sin 40 * t = 36.7 tan 40 Vo t = 36.7 tan 40 so back to 42 = Vo t + 4.9 t^2 now 42 = 36.7 tan 40 + 4.9 t^2 solve for t, time in the air, and go back and get the rest

*May 20, 2016*

**plz help asap**

they are d miles apart at the start Va + Vb = V V(1) = d V(3/4) = d-200 d(3/4) = d - 200 200 = d/4 d = 800

*May 20, 2016*

**help asap plz**

15 * 12 = 180 so The whole job requires 180 man days They worked for 4 days so did 15 * 4 = 60 man days they have 120 man days of work left 120 / n = 6 n = 20 men on the job so 5 new men joined

*May 20, 2016*

**HELP NEEDED ASAP**

dina takes 2 hours masha went 8 km in that 2 hours 8/2 = 4 km/hour

*May 20, 2016*

**maths**

(40/360)72

*May 20, 2016*

**Physics**

Draw a picture parallel ray from top bounces off and heads through center line at 25 cm from mirror ray through focus from top comes out parallel below rays intersect right below original so: same distance from mirror same height but upside down. check the old answers below by...

*May 19, 2016*

**Math**

Do you own a calculator? eg f(x) = 1/(x-2) if x = +2.5 f(2.5) = +2 if x = 2.1 f(2.1) = +10 if x = .001 f(2.001) = +1000 etc

*May 19, 2016*

**Algebra**

LOL - I wondered when you would ask. both are y, so 7 x + 5 = 3.5 x + 20 that is called "substitution" 3.5 x = 15 x = 4.29 go back and get y ------------------- you could also subtract the two equations to get rid of y 7x-3.5 x + 5-20 = 0 that is called "...

*May 17, 2016*

**Pre-Calculus**

F(t) = 20 * 1.6^t G(t) = 100 * 1.6^t = 5 F(t) once five times as many, always five times as many :)

*May 17, 2016*

**math**

v = k A h 24 = k 24 * 3 so k = 1/3 (this is not news by the way:) v = (1/3)(15)(7) = 35 cubic inches By the way: The volume of any shape with pointy top and straight sides is (1/3)(base area)(height) ---->cone, pyramid, whatever

*May 17, 2016*

**PHY101**

the final mass is 2200 Kg if it is totally inelastic and they stick to each other. east momentum 1200 * 90 = 2200 Ve north momentum 1000 * 90 = 2200 Vn |V| = sqrt (Ve^2+Vn^2) tan compass angle east of north = Ve/Vn

*May 17, 2016*

**I do not have access to your file**

That does not work.

*May 17, 2016*

**Is that right ?**

So you are asking some retired professor in Massachusetts who does not even know what country you are in ?

*May 17, 2016*

**Math**

-3m * m = -3m^2 -3m * 8 = -24 m now add

*May 17, 2016*

**math**

cost = 25 + 50 H now just put in 8 for H then put in 10 for H

*May 17, 2016*

**algebra 2**

in practice 0.5 in theory 0.25 difference = ?

*May 17, 2016*

**Math/algebra**

Watch out for difference between sample and total population standard deviations. Divide by 9 or divide by 10.

*May 17, 2016*

**Math/algebra**

http://www.mathsisfun.com/data/standard-deviation-calculator.html

*May 17, 2016*

**check english please.. romeo and juliet**

I am inclined to agree with you.

*May 17, 2016*

**LIMITS CALCULUS**

Oh, did not notice that. (-8)^(1/3) that is a complex number e^iT = cos T + i sin T -8 = 8 cos pi + 8 sin pi = 8 e^pi i (8 e^i pi)^(1/3) = 2 e^ipi/3 or 2 e^i(3pi/3) or 2e^i(5 pi/3) = 2(cos 60+ i sin 60) or = 2 (cos 180 + i sin 180) or = 2 (cos 300 + i sin 300) = 1 + 1.73 i or...

*May 17, 2016*

**LIMITS CALCULUS**

as x gets big the numerator is dominated by the -8 x^3 term as x gets big the denominator is dominated by the x^3 term so the numerator over the denominator ----> -8 x^3/x^3 = -8

*May 17, 2016*

**physics**

m = integral fro 0 to L of λ dx m= λo [ L + (1/3L^2)L^3 ] m= λo [ 4L/3 ] -------------------------------- Xcg = (1/m) λ x dx = (1/m) (x^4/4L^2 + x^2/2)λo = (1/m) (L^2)(3/4)λo = (3/4L)(3/4)L^2 = (9/16)L whew ------------------------------- for c ...

*May 16, 2016*

**Maths**

seventh term = sixth term * 3 eighth term = sixth term * 9 ninth term = sixth term * 27

*May 16, 2016*

**calculus**

hypotenuse = 2 adjacent = x so opposite = sqrt(4 - x^2) sin = sqrt(4-x^2) / 2

*May 16, 2016*

**Math**

Nah, when you multiply by 1.2 you do not get anything that big 6.3 * 1.2 = 7.56 one way to think about it: (6 + 0.3)(1 + 0.2) = 6(1 + 0.2) + 0.3(1 + 0.2) = 6 + 1.2 + 0.3 + .06 = 7.56

*May 16, 2016*