Thursday
December 8, 2016

Posts by Damon

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
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

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

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

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

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

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

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

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