Friday
October 28, 2016

# Posts by Damon

Total # Posts: 27,589

Probability and statistic
http://davidmlane.com/hyperstat/z_table.html
June 27, 2016

physics
60,000 /3600 = 16.7 m/s 45,000 /3600 = 12.5 m/s v =Vi + a t 12.5 = 16.7 + 10 a a = -0.42 meters/second^2
June 27, 2016

physics
d = (1/2) a t^2
June 27, 2016

Math
in the slope/intercept form: y = m x + b m is the slope b is the y axis intercept where x = 0 here the slope is positive 0.5 so the line goes up to the right from the point (0,-2) (and of course down to the left :)
June 27, 2016

Math
y = 35 + 15 x
June 27, 2016

maths
(x-3)(3x+2)=0 alpha = 3 beta = -2/3 so (x-9)(x-4/9) = y x^2 -9x -4x/9 + 4 = y y = x^2 - (85/9) x + 4
June 27, 2016

English
One says "at". I suppose if you live in a tunnel, you eat "in" it :) However is you say: "What about dinner in my house?", You probably mean instead of in my yard or garage.
June 26, 2016

GEOMETRY
p(a)+ p (b) - p(a and b) 1,2,3,or 4 out of 6 = 4/6 tail = 1/2 = 3/6 4/6 + 3/6 - 2/6 = 5/6
June 26, 2016

GEOMETRY
prob of first one blue = 5/16 now we have 15 in the bag prob of white = 5/15 = 1/3 so 5/16 * 1/3 = 5/39
June 26, 2016

GEOMETRY
Hey, it is time you should be able to do these.
June 26, 2016

GEOMETRY
A and B could be 6 A and C - impossible B and C - impossible
June 26, 2016

GEOMETRY
the attempts are independent so (3/7)^3
June 26, 2016

GEOMETRY
2 out of 15 2/15
June 26, 2016

math
18,000 * 1.07^18
June 26, 2016

GEOMETRY
p even = 3/6 = 1/2 p A = 1/3 they are independent so 1/2 * 1/3 = 1/6
June 26, 2016

Math
cos T * sin T = 1/4 so 2 cos T * sin T = 1/2 so sin 2 T = 1/2 thus 2 T = 30 deg or pi/6 radians T = pi/12 radians or 15 deg now cos * sin must be + so T in quadrant 1 or quadrant 3 so actually T = pi/12 or T = 13pi/12 which is 195 deg pi/12 + 13 pi/12 + (2pi+pi/12) = (1/12 +13...
June 26, 2016

Biology
http://shenndesigns.weebly.com/my-physical-trait---curly-hair.html half of each assuming no one has only a little curly so 4:4
June 26, 2016

maths
a b a + b = 9 a = (1/2) b ============================== (1/2) b + b = 9 so (3/2) b = 9 so b = 18/3 which is 6 which means a = 3 and a b is 36
June 26, 2016

math
3 of anything + 3 of the same thing = 6 of them 6/30 = 1/5
June 26, 2016

Science
.05 * 90 = 4.5 mL
June 26, 2016

math - incomplete problem statement
(L+3)(w+3) = 84 + L w L w + 3 L + 3 w + 9 = 84 + L w 3 L + 3 w = 75 need another piece of information to solve Suspect you were given how much longer it was than wide
June 25, 2016

Physics
time t at 80 time t at 40 80 t + 40 t = 60 120 t = 60 t = (1/2) hour at each speed distance = 80(1/2) + 40(1/2) = 60km av speed = 60 km/1 hour
June 25, 2016

physics
north = 400 - 400 = 0 west = 300 d = sqrt (0^2 + 300^2) = 300 I have a hunch you have a typo.
June 25, 2016

Physics
capacitance is charge per unit voltage 60/40=1.5 Farads
June 25, 2016

Maths Year 10
x = k - 5 k x = k(k-5) = k^2 - 5k
June 25, 2016

math
54 = 15 + 3.25 x
June 25, 2016

Science
Will all that NaCl dissolve? I suspect not.
June 25, 2016

math
12 - 3 = 9 21 - 12 = 9 hmmm x - 21 = 9 maybe or x = 30 etc
June 25, 2016

Mathematics
a - (2/5)a = 24 3a/5 = 24 a/5 = 8 a = 40 yes
June 25, 2016

CHEMISTRY
NO-3 ? , SO2-4 ?, PO3 -4 Where did you get these strange charges for the ions? eg PO3 normally -3 ASSUMING your strange valences: In +3 NO -3 then to be neutral InNO In+3 * 4 = +12 SO2-4 * 3 = -12 so In4(SO2)3 similarly In4 (PO3)4 But I suspect you have the original statement ...
June 24, 2016

trig
north = -3*14+2*14*cos 60 east = 2*14*sin 60 d^2 = north^2 + east^2
June 24, 2016

Math: PreCal
yes, amplitude is five and period is 3 pi when x = 0: y = 5 cos (-pi/6) = 5 (.866) that is not a max or a min or and x intercept However there is always a reflection about the points where the argument of the cos function is zero because cos -z = cos z that is when (4/6)x = pi...
June 24, 2016

physics
some point (0,y) on y axis between y = -3 and y = +6 field up = k(-12)/(6-y)^2 field down = k(-5)/(y-3)^2 so 12(y-3)^2 = 5(6-y)^2
June 22, 2016

physics
find the linear velocity of the car from v = a t then angular velocity = v/R
June 21, 2016

maths
Ah, there, on a new computer that would not let me post link unless I typed my Jiska name in :)
June 21, 2016

maths
http://www.mathsisfun.com/numbers/dividing-by-zero.html
June 21, 2016

English
4-1 and 4-2 are correct although 4-2 is unlikely. 4. and 4-3 are incorrect.
June 21, 2016

whoops, forgot what I did before
I mean a = (F/m)e^-(bt/m)
June 19, 2016

physic mechanic
Friction force, unlike gravitational or electrostatic is not directed toward a source like a center of mass or a charge. Friction is therefore not a central force. Did you get your earlier one about a = F/m (1- e^(bt/m) ) alright?
June 19, 2016

algebra
each year value = 0.92 value year before v = Vi (0.92)^n v = 25,000 (0.92)^6
June 19, 2016

Scient
a mL of water is a gram 4.5 / x = .09 x = 50 grams water remains so 450 grams evaporated
June 18, 2016

Physics
7 m * 2 v = 14 m v (1/2)(7m)(2v)^2 = (1/2)(7)(4) mv^2 = 28 * (1/2)m v^2
June 18, 2016

Physics (Normal force and static coefficient)
F down slope = m g sin 42 = 2 * 9.8 * sin 42 = 13.1 Newtons down the slope so 13.1 = mu m g cos 42 or sin 42 = mu cos 42 mu = tan 42 mu = 0.900 At least 0.900 could be more
June 18, 2016

Maths
J = A - 15 J+10 = (1/2)(A+10) A - 15 + 10 = A/2 + 5 A/2 = 10 A = 20 J = 5 ========== check 2(5+10) = 20+10 30 = 30 sure enough
June 18, 2016

Math
In quad 2 sin is + cos is - of course we can look up the angle knowing the tangent and then find the sin etc but that is too easy. tan T = -5 = sin T/cos T cos T = sqrt (1 - sin^2 T) so -5 = sin T / sqrt(1-sin^2 T) 25 (1-sin^2 T ) = sin^2 T 25 = 26 sin^2 T sin^2 T = 25/26 sin ...
June 17, 2016

Geo Quiz
No way you could help the guy below you, Momen, who asked a far more difficult question luckily answered by Bob Pursley elsewhere.
June 17, 2016

Geo Quiz
All of your choices are nonsense the way you typed them without parentheses (x+3)^2 + (y-6)^2 = 25
June 17, 2016

Geo Final
surface area is 6 times area of one face = 6 (9) = 54
June 17, 2016

social studies.
You do not need help. You are doing just fine. For number four I might say the poor unemployed people of the country rather than the Republic itself.
June 17, 2016

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